GeometricField::dimensionedInteralFieldRef() -> GeometricField::ref()

In order to simplify expressions involving dimensioned internal field it
is preferable to use a simpler access convention.  Given that
GeometricField is derived from DimensionedField it is simply a matter of
de-referencing this underlying type unlike the boundary field which is
peripheral information.  For consistency with the new convention in
"tmp"  "dimensionedInteralFieldRef()" has been renamed "ref()".