Make improvements to vtkSMMapProperty and subclasses

This makes improvements and fixes some issues with vtkSMMapProperty
and its subclass (vtkSMDoubleMapProperty).

See ParaView bug #14205.

Change-Id: Ibd3b1d21f53224516477b46b1bfdf6e14f8a4fa3
Merge topic '14205-map-property-improvements' into next

ef5fd0e Make improvements to vtkSMMapProperty and subclasses