Improve feedback when checking refinement between models with different alphabets
When checking refinement (menu MTS/Check) between two models that have different alphabets you get a horrible error.
Eg.
Does model [PRIMES] refine model [PRIMES_SPEC] ? Verifying...
**** Runtime Exception: java.lang.IllegalArgumentException: The models are not comparab
When it should no produce an exception and simply say that the models have different alphabets and even show the alphabets if possible.