#1220 CIF to mCRL2: support input variables + some other small changes

• Best to review per commit.
• End-user visible changes for the CIF to mCRL2 transformer:
  • It now supports input variables.
  • Fixed the "Generate 'value' actions" option description.
  • Use the proper tool name for precondition violation reports.
  • Improve header comment in generated mCRL2 files.
  • Improved comment for value actions in generated mCRL2 files.
  • Improve multiple initial states 'sum' conditions, to not have unnecessary parentheses.
  • Small documentation improvement for the "Generate 'value' actions".
• Other changes in the CIF to mCRL2 transformer:
  • Use Lists.single more to reduce code clutter.
  • determineValueActionVars: simpler code for determining set of names.
  • Renamed addProcessExprForValueActVar to addProcessExprForVarWithValueAct.
  • addProcessExprForVarWithValueAct: fixed JavaDoc.
  • Throw AssertionError instead of RuntimeException.
  • No need to normalize types, as pre-processing takes care of that.

Addresses #1220 (closed)