Feature mesh stitching

See merge request OpenFOAM-plus!159

Improvements to HashTable internals

See merge request OpenFOAM-plus!158

- make single-parameter construct (label) explicit
- consolidate iterators
- slightly reduced overhead for some HashSet types
- improved resizing behaviour
- compact output for empty Ptr hashes

- unused, unmaintained and slower than the regular HashTable

- the zero::null and one::null sub-classes add an additional null
  output adapter.

  The function of the nil class (special-purpose class only used for
  HashSet) is now taken by zero::null.

- use (value <= VSMALL) instead of (value < VSMALL) for consistency
  with what equal(value, 0) delivers.

- add -compiler=NAME option to remove a build or platforms directory
  corresponding to any specified compiler on the current arch.

- when -compiler or -compiler=NAME is specified, also clean related
  sub-directories as well. This will cleanup mpi-related directory.

- consistent with C++ STL conventions, the reverse iterators should
  use operator++ to transit the list from rbegin() to rend().

  The previous implementation used raw pointers, which meant that they
  had the opposite behaviour: operator-- to transit from rbegin() to
  rend().

  The updated version only has operator++ defined, thus the compiler
  should catch any possible instances where people were using the old
  (incorrect) versions.

- updated forAllReverseIters() and forAllConstReverseIters() macros to
  be consistent with new implementation and with C++ STL conventions.

- forAllReverseIters and forAllReverseConstIters macros
- stdFoam::rbegin(), stdFoam::rend()
  stdFoam::crbegin(), stdFoam::crend()

Feature dictionary scoping lvalue

See merge request OpenFOAM-plus!124

- previously using a top-level #include would inadvertently remove the
  original header

Style list methods

See merge request OpenFOAM-plus!157

- this increases the flexibility of the interface

- Add stringOps 'natural' string sorting comparison.
  Digits are sorted in their natural order, which means that
      (file10.txt file05.txt file2.txt)
  are sorted as
      (file2.txt file05.txt file10.txt)

STYLE: consistent naming of template parameters for comparators

  - Compare for normal binary predicates
  - ListComparePredicate for list compare binary predicates

- similar to word::validate to allow stripping of invalid characters
  without triggering a FatalError.

- use this validated fileName in Foam::readDir to avoid problems when
  a directory contains files with invalid characters in their names

- adjust rmDir to handle filenames with invalid characters

- fileName::equals() static method to compare strings while ignoring
  any differences that are solely due to duplicate slashes

- more consistent naming:
  * Versions that hold and manage their own memory:
      IListStream, OListStream

  * Versions that reference a fixed size external memory:
      UIListStream, UOListStream

- use List storage instead of DynamicList within OListStream.
  Avoids duplicate bookkeeping, more direct handling of resizing.

- The problem occurs when using atof to parse values such as "1e-39"
  since this is out of range for a float and _can_ set errno to
  ERANGE.

  Similar to parsing of integers, now parse with the longest floating
  point representation "long double" via strtold (guaranteed to be
  part of C++11) and verify against the respective VGREAT values for
  overflow. Treat anything smaller than VSMALL to be zero.

- makes it accessible for containers that manage their own storage
  and derive directly from UList.

- DynamicList::min_size() method to access the corresponding
  SizeMin template parameter.

- ensure consistency in the reserve size for the constructor

      DynamicList<..> lst(N);

  now has identical sizing as

      DynamicList<..> lst();
      reserve(N);

ENH: Arrhenius viscocity model for incompressible viscocity

See merge request OpenFOAM-plus!155