Not all exposed to python code yet

This commit is pretty large because it contains two separate but interrelated changes:
- Rewrite the function argument handling code (callCompiledFunction and resolveCLFunc)
  into a single callFunc that does its own rewriting, and support the new features.
-- this required a change of data representations, so instead of having each function
   consist of variants with unrelated signatures, we can only have a single signature,
   but multiple type specializations of that signature
- To do that, had to rewrite all of the stdlib functions that used signature-variation
  (ex range1 + range2 + range3) to be a single function that took default arguments, and
  then took action appropriately.