- allows localized extension of functionality

- improved the selection mechanism to include using a bitSet
  cell selection (more efficient and convenient).

  Use templated implementation internally to remove the previous
  reliance on a NullObject.

- assignment operators return a value, for consistency with bool.

- partial revert of DEFAULT_TRUE, DEFAULT_FALSE, to reduce complexity.

Eg,
    #define FOAM_CONFIGURED_PROJECT_ETC "/usr/share/openfoam/etc"

This provides some easy to file patching locations, but is not yet
integrated in the build system at all.

- in some circumstances we need to pass a bool value upwards to the
  caller and know if the true/false value was set based on real input
  or is a default value.

  Eg, in the object::read() we might normally have

     enabled_(dict.readIfPresent(key, true));

  but would lose information about why the value is true/false.

  We can change that by using

     enabled_(dict.readIfPresent<Switch>(key, Switch::DEFAULT_ON));

  After which we can use this information is testing.

      if
      (
          child.enabled().nonDefault()
        ? child.enabled()
        : parent.enabled()
      )
      { ... }

   And thus enable output if the parent requested it explicitly or by
   default and it has not been explicitly disabled in the child.

  No difference when testing as a bool and the text representation
  of DEFAULT_ON / DEFAULT_OFF will simply be "true" / "false".

ENH: add construction of Switch from dictionary (similar to Enum)

- avoids removal of files and the dummy fallback

Feature snappy hex mesh check

See merge request OpenFOAM-plus!229

- as well as being more convenient to find, this is necessary when the
  OpenFOAM installation is without sources or tutorials

- older emacs tools into legacy
- old process tools

* Less frequently used scripts into bin/tools/

  - findEmptyMake
  - foamAllHC
  - foamUpdateCaseFileHeader

* Infrastructure file (only used by foamNewApp)

  - wmake/wmakeFilesAndOptions -> wmake/scripts/wmakeFilesAndOptions

* Merge wmakeRoot convenience as 'wmake -pwd'
* Remove obsolete wmakePrintBuild (superseded by wmakeBuildInfo)
* Remove unused mergeHistory file

Previously silently accepted '-o' as being equivalent to '-output',
but the former could be misinterpreted meaning an output file (which
it is not) instead of an output directory.

- instead of

      WM_COMPILER=GccKNL WM_COMPILE_OPTION=Opt

      -> linux64GccKNLDPInt32Opt

  now specify

      WM_COMPILER=Gcc  WM_COMPILE_OPTION=OptKNL

      -> linux64GccDPInt32OptKNL

This makes it easier (and more obvious) for adding different tweaks
without needing to generate too many files.
Eg,

    cd wmake/rules/linux64Gcc

    cp cOpt   cOptBdw
    cp c++Opt c++OptBdw

    edit these two files and then use WM_COMPILE_OPTION=OptBdw

CONFIG: provide some default c/c++ flags in General compiler rules

- can make is easier when deriving new compile options, and ensures
  that '-02' is enabled as an initial default.

- finds the correct root directory location before creating
  the lnInclude directory

  Eg,

  from within something like src/finiteVolume/fields/fvPatchFields/..

      wmakeLnInclude -update -root

  it backtracks to find the top-level directory with Make/
  and makes the lnInclude directory there:

    Using /home/mark/openfoam/OpenFOAM-plus/src/finiteVolume
        ln: /home/mark/openfoam/OpenFOAM-plus/src/finiteVolume/lnInclude

- Can result in inadvertent conversions where the user should really
  know or check if the pointer is valid prior to using.

- Still have several places to fix that are using the deprecated copy
  construct and copy assignment

- workaround for some old compilers many years ago, but no longer relevant

- in the previous version, a specification such as (U "U.*")
  would have selected the field name twice for writing

- can also be used for other purposes.
  Eg,

      if (ListOps::found(list, matcher))
      {
         ...
      }

  vs.

      if (!findStrings(matcher, list).empty())
      {
         ...
      }

- add compile-time detection of deprecated findIndex() function

- replace occurrences of findIndex() with the equivalent container
  method

- simply a functionObject with an additional Time reference, which is
  a combination frequently used by concrete functionObjects

- use for-range when iterating
- dictionary access/search methods
- autoPtr for memory management

- changed the sectorCoeffs keyword to 'point' from 'axisPt'
  for more similarity with other dictionaries.
  Continue to accept 'axisPt' for compatibility.