Relax constraint aimed at precedence of the included use cases

[jiri-vinarek]

Current version of FOAM tool has following limitation: When use cases A includes use case B, then all use cases that has use case B in its precedence (prec(B)) must be also in precedence of A (prec(B) must be subset of prec(A)).

Reason for this restriction is an ambiguity of the precedence relation within include - it is not clear when the preceded use case of the included use case must be executed.

This limitation restricts writing of the "high-level" use cases.

Solution is to relax this restriction - use case that is in prec(B) must be in prec(A) OR it had to be executed before the inclusion (by prior include).
For each included use case X with non-empty precedence set following formula will be added:

LTL exec(X) -> O ( exec(prec(X)[0]) & exec(prec(X)[1]) & ... & exec(prec(X)[n]) )