Misc generic improvements

[Vindaar]

Minor cleanup of the macro logic code and removal of dead code as well as some improvements:

• genColumn -> defColumn
• toDf now works with generic arguments as long as a matching column type is defined

Changelog:

* v0.3.3
- define =ScalarLike= concept to match types that can be converted to
  =float= via =.float= for e.g. units to have a =%~= Value conversion
  for them
- minor cleanup of macro logic
- rename =genColumn= to =defColumn=
- =toDf= now supports assignment of generic arguments as well, as long
  as the column types required have been generated already.
- =defColumn= now generates all combinations of the given types
- fixes some issues with =unionType= getting confused
- makes =toColumn= work correctly with =array=