Those libraries should instead be imported from the mmt-api module, on which this module still depends.

Also changed simplifier to accept additional flag that prevents substitution of variables

to overcome syntax errors

- new TermGeneratorTest.scala contains main for testing purposes
- SFOLTermGenerator requires for init now additionally MPath and Int. The Int is the max syntax tree depth one wants to generate.
- Termgeneration is now function. newTerm() returns single term.
- Generator now supports generation of Stream[Term]. Use makeTerms() for that.