Feature post release cleaning

See merge request !122

- as of v1706
  extractFromSurfaceCoeffs { ... } is an optional subdictionary

- replace duplicate code with global bounds enums and Enum

- if the enum name is not found, then warn and return the default.

- use typedefs and new features/methods
- file-scope template to avoid code duplication.

- make the purpose of various parts clearer

- can now suppress prefixing an underscore to leading digits.

- allows configuration without an environment variable.
  For compatibility still respect FOAM_SIGFPE and FOAM_SETNAN
  env-variables

- The env-variables are now treated as true/false switch values.
  Previously there was just a check for env exists or not, but this
  can be fairly fragile for a user's environment.

- allows configuration without an environment variable.
  For compatibility still respect MPI_BUFFER_SIZE env-variable.

ENH: add degToRad() multiplier (useful for scalar fields)

- use degToRad() functions throughout instead of scattered local solutions

- avoid loading surface fields if there are no faceZones

- avoid pointMesh if there are no appropriate point fields

- erroneous double logic for subset meshes.

  The underlying vtk::vtuCells uses a cellMap to map into a global
  field, which also allows handling of decomposed polyhedral cells.

  If a mesh subset is involved (eg, cellSet, cellZone), then the
  set/zone cellMap can be used to ensure that the original number is
  properly adjusted. For foamToVTK, the meshSubsetHelper already
  does the subsetting and is used when loading fields.

  Does not affect ParaView reader module since there we work on the
  full field and do the subsetting manually (using the cellMap).

- use 1024 instead of 1000 since it will be changed internally to 1024 anyhow.

- use separate constructor for ignore-case option (cf. wordRe treatment)

- constructors/destructor now inline.

- make some IOobject writing routines non-templated.

- relocate more IOobject methods into the IOobjectI.H
  (generally cleanup the main header).

Merge develop into master for v1706 release

Closes #505, #509, #497, #502, #500, #498, #493, #492, #490, #485, #486, #484, #481, #480, #467, #473, #470, #466, #464, #463, #460, #462, #458, #418, #420, #391, #452, #454, #453, #439, #427, #415, #422, #414, #411, #400, #398, and #348

See merge request !121

STY: Fixing syntax in rhoPimpleDyMFoam/pEqn.H

by fvMesh.writeObject().