STYLE: more consistent use of dimensioned Zero

- affects random integer ranges.
  Simpler to extend the range by one and floor (truncate) instead of
  rounding using odd intervals.

- replace SortableList with sortedOrder, to reduce some overhead

TODO: migrate singleCellFvMesh into simplified mesh framework (?)

Merge branch 'develop-pre-release' of develop.openfoam.com:Development/OpenFOAM-plus into develop-pre-release

- samples on cell centres, can optionally limit based on a bounding box.
  Can be used, for example, to extract volume fields into CSV format.

- add some more documentation

Merge branch 'develop-pre-release' of develop.openfoam.com:Development/OpenFOAM-plus into develop-pre-release

- improve handling of model: ... line

- simplify parsing of xxx element: ... lines

- start/end values were underrepresented due to rounding.
  Now extend the range to include -0.5 and +0.5 beyond the usual
  range to ensure the same number density.

Merge branch 'develop-pre-release' of develop.openfoam.com:Development/OpenFOAM-plus into develop-pre-release

Merge branch 'develop-pre-release' of develop.openfoam.com:Development/OpenFOAM-plus into develop-pre-release