Subclass Assumptions Predicate from FOL

- [ ] Subclass assumptions.Predicate from FOL.Callable and rename it to AssumptionsPredicate.
- [ ] Subclass assumptions.AppliedPredicate from FOL.Applied and rename it to AppliedAssumptionsPredicate.
- [ ] Rename Function and AppliedFunction in FOL.
I would subclass Predicate. That seems clearer, and assumedly its apply would be useful here.