- use outerProduct for sumSqr() for consistency with sqr()

- for most functions the input type and return type are identical,
  but MinMax, sumMag are not.

- previously returned scalar, but now return pTraits cmptType
  which is the same as scalarProduct / outerProduct type.

- Global functions are unary or combining binary functions, which are
  defined in MinMax.H (MinMaxOps.H).

  There are also global reduction functions (gMinMax, gMinMaxMag)
  as well as supporting 'Op' classes:

  - minMaxOp, minMaxEqOp, minMaxMagOp, minMaxMagEqOp

  Since the result of the functions represents a content reduction
  into a single MinMax<T> value (a min/max pair), field operations
  returning a field simply do not make sense.

- Implemented for lists, fields, field-fields, DimensionedField,
  GeometricField (parallel reducing, with boundaries).

- Since the minMax evaluates during its operation, this makes it more
  efficient for cases where both min/max values are required since it
  avoids looping twice through the data.

  * Changed GeometricField writeMinMax accordingly.

ENH: clip as field function

- clipping provides a more efficient, single-pass operation to apply
  lower/upper limits on single or multiple values.

  Examples,

    scalarMinMax limiter(0, 1);

    limiter.clip(value)

       -> returns a const-ref to the value if within the range, or else
          returns the appropriate lower/upper limit

    limiter.inplaceClip(value)

       -> Modifies the value if necessary to be within lower/upper limit

  Function calls

    clip(value, limiter)

       -> returns a copy after applying lower/upper limit

    clip(values, limiter)

       -> returns a tmp<Field> of clipped values

Foam::direction is an unsigned type which makes it easier for the
compiler to pickup and report errors in the instantiation of
VectorSpaces and associated types.

To compile with 64bit labels set

WM_LABEL_SIZE=64

in ~/OpenFOAM/dev/prefs.sh

source ~/.bashrc

then Allwmake in OpenFOAM-dev.

This will build into for example OpenFOAM-dev/platforms/linux64ClangDPInt64Opt

If WM_LABEL_SIZE is unset or set to 32:

WM_LABEL_SIZE=32

the build would be placed into OpenFOAM-dev/platforms/linux64ClangDPInt32Opt

Thus both 32bit and 64bit label builds can coexist without problem.

(originating from polyMesh::comm() and processorPolyPatch::comm())

LduMatrix: Added support for both component-coupled and component-independent forms of PCG and PBiCG

This reverts commit c5bea524.

This reverts commit b18f6cc1.