#948 CIF to mCRL2 supports div/mod on positive divisors

• Best to review per commit.
• End-user visible changes:
  • CIF to mCRL2 supports div and mod on positive divisors.
• Other changes:
  • ExprNoSpecificBinaryExprsCheck: remove disallowing div/mod on integers, as it is the same as disallowing the operator altogether (they can only be applied to integers). I did keep the ranged/rangeless variants, as that may still be useful.
  • ExprNoSpecificBinaryExprsCheck now supports disallowing div and mod with a non-positive divisor.

Closes #948 (closed)