removed excess printing function (if needed later it can just be picked up from initial commit)
Changed some minor names.

Concrete -> Constant (When we know a type it is a constant, as opposed to variable)
PrTerm/Cterm -> PrimitiveTerm, TimeTerm
Separated unbound and bound time variables in the AST. Increases the certainty we can't mix bound time instances and unbound time instances.
Renamed type constructors/data constructors to match new separation of time variables.