Allow generate objects to use any arrayhandle type.

This includes constant value and counting array handles.
Allow schedulers to use visit index when we have two args.

Previously we had to have more than two args to parse the visit
index, which was an oversight.
Custom array handles like counting and constant now have concept maps.

This means we can upload and use these custom array handles as
Field arguments to worklets.
Simplify including all concepts maps to schedulers.
Add tetrahedralize worklet to verify constant value classify works.
Expand Sine unit test to verify counting and constant array handles.

We are going to use sine to verify that all custom handles properly
work as arguments to a worklet.
Merge branch 'support_custom_classify_types'