- marks if the value is considered to be independent of 'x'.
Propagate into PatchFunction1 instead ad hoc checks there.
- adjust method name in PatchFunction1 to 'whichDb()' to reflect
final changes in Function1 method names.
ENH: add a Function1 'none' placeholder function
- This is principally useful for interfaces that expect a Function1
but where it is not necessarily used by a particular submodel.
TUT: update Function1 creation to use objectRegistry