- clearer, more consistent parameter naming, which helps when
  maintaining different field function types (eg, DimensionedFields,
  GeometricFields)

- provide reuseTmpGeometricField::New taking a reference (not a tmp),
  with forwarding. This helps centralise naming and acquisition etc

- split binary function macros into transform/interface
  for easier support of different transform loops.

- initial field macros for looping over ternaries