consolidate surfaceFormats for reading/writing triSurface

See merge request !174

preliminary improvements for externalCoupled

See merge request !175

- similar idea as subCycleTime but without sub-dividing the time
  interval or incrementing time itself

- waitForSlave now return a Time::stopAtControls enumeration:

    unknown:     when lockfile has no specially recognized content.
    endTime:     when lockfile contains "status=done"
    writeNow:    when lockfile contains "action=writeNow"
    nextWrite:   when lockfile contains "action=nextWrite"
    noWriteNow:  when lockfile contains "action=noWriteNow"

These values can be used by the caller to terminate the master
(OpenFOAM) as desired in response to information placed there by the
slave process.

- use a Pair<scalar> with first() / last() residuals

- expose the names of write and stopAt controls for reuse elsewhere and
  provide a stopAtControls enum for 'unknown'

- track the requested number of sub-cycles (was previously a bool)

- found() method for consistency with other classes

- operator()(name, deflt) for similarity to lookupOrDefault,
  but without a dictionary

- the readList<T>(Istream&) function was introduced to handle command
  -options with either a single or a list value, but was also used for
  the #remove dictionary directive. However, the parsing was fragile
  if the list did not start with a '('.
  Now handle command-line arg/option list directly (via ITstream)
  and #remove with special-purpose reading of a string or word list.

  This removes ambiguity and reduces potential future problems.

STYLE: use ITstream instead of IStringStream for command-line lookups

- parses directly to a tokenList without a string copy.

- eliminates previous code duplication and improves maintainability

- unknown options or missing option values now emit a shorter message
  without the entire usage. This makes it easier to identify the errors
  and is better aligned with the behaviour of GNU system tools.

  ====
     $ simpleFoam -case
     Using: OpenFOAM-plus (see www.OpenFOAM.com)
     Build: plus-01234

     Error: option '-case' requires an argument

     See 'simpleFoam -help' for usage
  ====

- provide for reduced (-help) and full (-help-full) usage information.
  In many cases the reduced usage provided sufficient and easier
  to find the information.

- make -srcDoc an alias for -doc-source

- no warnings about option aliases for future dates.

- stricter and robuster than previous solution using List::readList
  since the option input can be fully tokenized prior to list
  conversion.

- split now optionally retains empty substrings.
  Added split on fixed field width.

- Foam::name() now formats directly into string buffer, which a
  removes one layer of copying and also avoids using a non-constexpr
  in the temporary.

STYLE: explicit type narrowing on zero-padded output for ensight

- not maintained and less functionality than ccmToFoam.

Feature arglist option aliases

See merge request !172

- can be used for adjusting option names between versions

- in most cases already checked valid() so don't need additional check
  for setting an existing pointer

- browser is spawned as a background process to avoid blocking the
  command-line

- allows (for example) splitting a user string on whitespace and
  passing this to system as a list of arguments, thus bypassing any
  implicit use of 'sh'.

- system() with optional background, for spawning processes.

- this makes them applicable to Foam::string, Foam::word etc

ENH: improvements to CStringList

- add strings() sublist variant which can be useful when handling
  command arguments separately

- add construct from SubStrings.

Feature multiple stitch mesh (wp04)

See merge request !164

- the dictionary-driven variant of stitchMesh allows sequential
  application of 'stitch' operation with requiring intermediate
  writing to disk.

- Without arguments:
  * stitchMesh uses a system/stitchMeshDict or -dict dict

- With arguments:
  * master/slave patches specified on the command-line as in previous
    versions.

Consistency update for list typedefs

See merge request !171

- in rare cases we may wish to have command-line arguments that are
  non-mandatory. This can now be reflected in the usage output, provided
  that the argList::nonMandatoryArgs() has been used.

- added setRootCaseNonMandatoryArgs.H that applies the
  argList::nonMandatoryArgs() settings and otherwise performs largely
  as per setRootCase.H, except that the check for mandatory arguments
  is deferred to later user code.

- constructor for empty cell/face/point Zones, with contents to be
  transferred in later.

- ZoneMesh::operator(const word&) to return existing zone or a new empty one.

cellModel enumerations

See merge request !170

- this provides a better typesafe means of locating predefined cell
  models than relying on strings. The lookup is now ptr() or ref()
  directly. The lookup functions behave like on-demand singletons when
  loading "etc/cellModels".

  Functionality is now located entirely in cellModel but a forwarding
  version of cellModeller is provided for API (but not ABI) compatibility
  with older existing user code.

STYLE: use constexpr for cellMatcher constants

- warn or fatal if Pstream::init or Pstream::exit are called multiple
  times.

- additional Pstream::initNull method as failsafe to initialize MPI
  when the underlying OpenFOAM process is not running in parallel but
  the application still needs MPI.

- Pstream::exit() can now also be called without having used MPI::init(),
  which means it can be used to cleanup serial process or for
  applications that used the special purpose Pstream::initNull()
  mechanism.