This is controlled by the setting maxCommsSize in etc/controlDict which
specifies the max number of bytes per exchange. If set to <= 0 it
is ignored. This max size of messages is important when doing e.g.
load balancing which can send over whole meshes.

ENH: improve objectRegistry functionality (issue #322)

- Recursive searching for objects within a registry is now optional
  (previous it was always done).

  A recursive search effectively blocks the construction of sub-sub-registries
  if their names are 'masked' by some parent level sub-registry with
  the same name! (BUG)

- Recursive search is now turned OFF by default, which makes it consistent
  with dictionary and probably causes the least number of surprises.

----
Various new convenience methods added:

lookupObjectRef()
- returns a non-const reference.
  For example,

      volScalarField& U = mesh().lookupObjectRef<volScalarField>("U");

  Instead of

      volScalarField& U = const_cast<volScalarField&>
      (
          mesh().lookupObject<volScalarField>("U")
      );

--
lookupObjectPtr()
- returns a const pointer, and nullptr on failure.
  For example,

      const volScalarField* Uptr = mesh().lookupObjectPtr<volScalarField>("U");
      if (Uptr)
      {
          const volScalarField& U = *Uptr;
          ...
      }

  Instead of

      if (mesh().foundObject<volScalarField>("U"))
      {
          const volScalarField& U = mesh().lookupObject<volScalarField>("U");
          ...
      }

--
lookupObjectRefPtr()
- returns a non-const pointer, and nullptr on failure.
  For example,

      volScalarField* Uptr = mesh().lookupObjectRefPtr<volScalarField>("U");
      if (Uptr)
      {
          volScalarField& U = *Uptr;  // use as reference
          (*Uptr) = ...;              // or use directly
      }

  Instead of

      if (mesh().foundObject<volScalarField>("U"))
      {
          volScalarField& U = const_cast<volScalarField&>
          (
              mesh().lookupObject<volScalarField>("U")
          );
      }

--
sortedNames()
- now works with template parameters and with regular expression
  matching as well.
  For example,

      wordList names  = mesh().sortedNames();
      wordList fields = mesh().sortedName<volScalarField>();

  Instead of

      wordList names  = mesh().sortedNames();
      wordList fields = mesh().names<volScalarField>();
      Foam::sort(fields);

--

See merge request !83

runTimePostProcessing FO camera update

- Removed the camera 'mode'
    - The (old) static camera was only appropriate when parallel
      projection was inactive, and the view was centred at (0 0 0)
    - Camera input now always requires 'position' and 'focalPoint'
    - Clip box is now optional.  Note that this is applied after the
      camera
      set-up and so will override the camera position
    - View angle is only appropriate when not using parallel projection
    - Zoom now required, applied after all other operations
      - 1 = do nothing, >1 = zoom in, <1 = zoom out

    Example input:

```
        camera
        {
            // Total number of frames to generate
            nFrameTotal 1;

            // Parallel projection flag
            parallelProjection no;

            focalPoint  (0 0 0);
            up          (0 1 0);
            position    (0 0 1);

            // Optional entries
            clipBox     (-0.0206 -0.0254 -0.0005) (0.29 0.0254 0.0005);
            viewAngle   20;
            zoom        1.1;
        }
```

See merge request !81

Conflicts:
	src/TurbulenceModels/compressible/turbulentFluidThermoModels/derivedFvPatchFields/outletMappedUniformInletHeatAddition/outletMappedUniformInletHeatAdditionFvPatchField.H

- make it easier to transfer triSurface information into MeshedSurface
  etc.

- identical code was present in surfaceCheck (original source),
  and isoSurface, isoSurfaceCell (copies).

- add in a MeshedSurface<face> variant as well, since this will likely
  be needed in the near future

- add writeObject method

- otherwise difficult to avoid auto-write etc.

- propagate similar changes to MeshedSurfaceAllocator, where is makes
  the most sense.

- Should be updating references (shallow copy), but triggers a deep copy
  instead. Likely introduced by ac71f865.

- other sampled surface types use meshCells() throughout.
  Only cuttingPlane was different.

- This is simply the normal helmet geometry, but shifted to where a
  passenger head may be. It can be used for surface sampling etc.

- The null constructor already creates a dimensionless Zero,
  but named "undefined".

  Provide an constructor for a dimensioned Zero,
  but named "0" for universal clarity to its value.

- provide additional filtering methods on names(), sortedNames()
  For example,

      IOobjectList objects = ...;
      wordReList selection = ...;

      objects.sortedNames(VolFieldType::typeName, selection);

- Recursive searching for objects within a registry is now optional
  (previous it was always done).

  A recursive search effectively blocks the construction of sub-sub-registries
  if their names are 'masked' by some parent level sub-registry with
  the same name! (BUG)

- Recursive search is now turned OFF by default, which makes it consistent
  with dictionary and probably causes the least number of surprises.

----
Various new convenience methods added:

lookupObjectRef()
- returns a non-const reference.
  For example,

      volScalarField& U = mesh().lookupObjectRef<volScalarField>("U");

  Instead of

      volScalarField& U = const_cast<volScalarField&>
      (
          mesh().lookupObject<volScalarField>("U")
      );

--
lookupObjectPtr()
- returns a const pointer, and nullptr on failure.
  For example,

      const volScalarField* Uptr = mesh().lookupObjectPtr<volScalarField>("U");
      if (Uptr)
      {
          const volScalarField& U = *Uptr;
          ...
      }

  Instead of

      if (mesh().foundObject<volScalarField>("U"))
      {
          const volScalarField& U = mesh().lookupObject<volScalarField>("U");
          ...
      }

--
lookupObjectRefPtr()
- returns a non-const pointer, and nullptr on failure.
  For example,

      volScalarField* Uptr = mesh().lookupObjectRefPtr<volScalarField>("U");
      if (Uptr)
      {
          volScalarField& U = *Uptr;  // use as reference
          (*Uptr) = ...;              // or use directly
      }

  Instead of

      if (mesh().foundObject<volScalarField>("U"))
      {
          volScalarField& U = const_cast<volScalarField&>
          (
              mesh().lookupObject<volScalarField>("U")
          );
      }

--
sortedNames()
- now works with template parameters and with regular expression
  matching as well.
  For example,

      wordList names  = mesh().sortedNames();
      wordList fields = mesh().sortedName<volScalarField>();

  Instead of

      wordList names  = mesh().sortedNames();
      wordList fields = mesh().names<volScalarField>();
      Foam::sort(fields);

--

- test clearly shows failure to insert a sub-registry when it has
  the same name as one of the parent sub-registry.

- the user might otherwise be unaware of the changed location

- both are typedefs for UList<label>

- was using direct face ids instead of appropriate sub-lists
- also removed typo that wasn't helping much either

- remove remnant nullptr check