#1045 CIF simulator: add execution mode

• Best to review per commit.
• End-user visible changes:
  • The CIF simulator now has an 'Execution mode' option, to enable execution mode. It is disabled by default. With execution mode, the simulator adheres to the execution scheme defined by the CIF controller properties checker.
  • Small textual fix in CIF controller properties checker's execution scheme documentation.
  • Small improvements to CIF to CIF linearization, CIF code generator and PLCgen documentation.
• Notes:
  • There are several preconditions for using the execution mode. Some could maybe be relaxed in the future, but for a first version, these seem fine.
  • Since we may relax some preconditions later, I could imagine having another value for the execution mode option, that is not strictly compatible. I therefore opted for an enum-based option, rather than a boolean option.

Closes #1045 (closed)