- align timeVaryingMappedFixedValuePointPatchField keywords with
  MappedFile

STYLE: minor cleanup of pointToPointPlanarInterpolation

BUG: incorrect keyword for timeVaryingMappedFixedValuePointPatchField

- lookup should be "fieldTable" (not "fieldTableName") for consistency
  with the output and other BCs. (Bug introduced by a623ab42)