- this is consistent with compiler defaults, and helps Darwin users

- resolve in favour of "inline explicit", which had marginally more
  uses and provides consistent prefixing for inline methods.

- make the purpose more explicit, and reduces some work for the
  compiler as well.

- improves backward compatibility and more naming consistency.
  Retain setMany(iter1, iter2) to avoid ambiguity with the
  PackedList::set(index, value) method.

- required for std::iterator_traits specialization, which is used by
  the std::max_element algorithm on Darwin.

- move constructable
- factory methods: New, NewFrom
- reset methods

- consistency with make and more succinct.

- reduce code duplication in findEtcFiles.

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

Update QDot dimensions for diffusionMulticomponent

Basic directional refinement:
- only for coordinate aligned meshes
- only for refinementRegions
See the mesh/snappyHexMesh/aerofoilNACA0012_directionalRefinement
tutorial.

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