Better support for CVC4

- Cast integer literals to reals if returned in a model for a
  real-valued term or variable
- Fail if using precise quantifier elimination or switching to it
Merge pull request #172 from chsticksel/develop

Better support for CVC4
Warn if using inductive step without BMC
Merge pull request #173 from chsticksel/develop

Warn if using inductive step without BMC
Explicit unrolling + fixed compression deactivation in step.
Removed obsolete functions in transSys.
Merge pull request #2 from AdrienChampion/feature_explicit-unrolling

Explicit unrolling of the state variables