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/functionObjects/field/externalCoupled/externalCoupledTemperatureMixed/externalCoupledTemperatureMixedFvPatchScalarField.C

@@ -160,7 +160,7 @@ externalCoupledTemperatureMixedFvPatchScalarField
         // or extrapolated value
         if (!this->readValueEntry(dict))
         {
-            fvPatchField<scalar>::operator=(this->patchInternalField());
+            fvPatchField<scalar>::patchInternalField(*this);
         }
 
         // Initialise as a fixed value