Proper Safety Check

[AntoniusW]

There currently is no correct and reliable safety check in place. Safety of rules is established only after normalization when the RuleGroundingOrder is running. There currently may be non-safe programs that are simply accepted yielding unexpected behaviour (wrong answers or throwing an exception).

A proper safety check should be put in place before the input program is transformed in any way.

[madmike200590]

Also handle proper error remark for scenario described in #286 here