ENH: place more patch field attributes under template invariant Base

- attributes such as assignable(), coupled() etc

- common patchField types: calculatedType(), zeroGradientType() etc.
  This simplifies reference to these types without actually needing a
  typed patchField version.

ENH: add some basic patchField types to fieldTypes namespace

- allows more general use of the names

ENH: set extrapolated/calculated from patchInternalField directly

- avoids intermediate tmp

src/OpenFOAM/fields/pointPatchFields/basic/zeroGradient/zeroGradientPointPatchField.C

@@ -27,15 +27,6 @@ License
 
 #include "zeroGradientPointPatchField.H"
 
-// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
-
-template<class Type>
-const Foam::word& Foam::pointPatchField<Type>::zeroGradientType()
-{
-    return Foam::zeroGradientPointPatchField<Type>::typeName;
-}
-
-
 // * * * * * * * * * * * * * * * Member Functions  * * * * * * * * * * * * * //
 
 template<class Type>