- provides a more uniform interface to string list operations etc

STYLE: more complete docs for keyType

- in preparation for using PackedBoolList

- useful for generating combined zones. Eg,

      cellZone combined
      (
          "combinedZone",
          czm.inZone(key).used(),
          ZoneI,
          *this
      );

ENH: adjust internal storage of PackedList to ensure that all unused
     internal storage elements are guaranteed to always be bit-wise
     zero. This makes the PackedBoolList implementation easier, and
     also greatly eases much of the book-keeping.
     Bits are now also zeroed on PackedList::clear()

Note: in PackedList, require packing at least 2 items otherwise it is
     more efficient to use a normal list.

picked up by a copyright change.

Exception: applyWallFunctionBoundaryConditions.C cannot split #include
directives.

Creates linear slope only from low and high elements around the sample
value, so rate will be discontinuous.  Would be better with higher
order gradient calculation.

STYLE: use findIndices instead of findAll for coordinateSystems