When specifying the averaging data, a new `windowType` option is
available, taking the values:

- none: no windowing
- approximate: past functionality (v1706 and earlier)
- exact: exact moving average - will store and write (for restart) all
  fields in the window

dictionary compatibility/migration methods

See merge request OpenFOAM-plus!162

- when dictionary keywords change between versions, the programmer
  can use these compatibility methods to help with migration.

    * csearchCompat, foundCompat, lookupEntryPtrCompat, lookupEntryCompat,
      lookupCompat, lookupOrDefaultCompat, readIfPresentCompat, ...

  They behave like their similarly named base versions, but accept an
  additional list of older keyword names augmented by a version number.
  For example,

      dict.readIfPresentCompat
      (
          "key", {{"olderName", 1612}, {"veryOld", 240}},
          myscalar
      );

   where 1612=OpenFOAM-v1612, 240=OpenFOAM-v2.4.x, etc.

- If the entry could be directly inserted: a pointer to the inserted entry.
- If a dictionary merge was required: a pointer to the dictionary that
  received the entry.
- Return nullptr on any type of insertion failure.

This change is code compatible with existing code since it only alters
a bool return value to be a pointer return value.

Improvements to token handling

See merge request OpenFOAM-plus!160

STYLE: Corrected file name in surface noise, added README file

See merge request OpenFOAM-plus!161

- simplify string output code

- improved memory alignment reduces overhead for Int32 compilation

- added move/swap semantics

- made the type() readonly in favour of setVariant() to allow change
  of variant within a particular storage representation.
  Eg, STRING -> VERBATIMSTRING.

- move append() single element to List and DynamicList

ENH: add stringOps::count to avoid unnecessary string conversions

- support send/receive with embedded '\0' characters

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.