The construction of some patch fields has been corrected so that the
patchType setting always propagates on mapping, IO, clone, etc...
Dictionary and mapping-based patch field constructors now call the
corresponding constructor from the base class, regardless of whether
dictionary settings or mapping are actually needed.
A "mappingRequired" flag has been added to some of the base constructors
in order to prevent unecessary mapping of field data and retain the
previous level of optimisation.
Resolves bug report https://bugs.openfoam.org/view.php?id=3144
