Let the SMT lib convert models to Z3-like models

The Model parser for SMT models is broken beyond repair
and this by-passes this. The code could be moved to the
model parser, but that's a refactoring for another day.
Also, the existing version already had multiple reparses
going on and this at least removes one of those.

Patch by Jeroen Ketema.
Remove dead code

Patch by Jeroen Ketema
Remove dead method argument

Patch by Jeroen Ketema
Merge.