NOT with operator == throws an exception during build time

[maxkratz]

NOT with operator == creates infeasible ILP problems. Example:

!mappings.n2n->filter(m | m.nodes().snode == self)->count() == 1

Problem:
expr + sub_1 >= 1 but there is somethin missing:
expr - sub_1 <= 1

Update: The build of such a constraint is currently not supported. The transformation throws an exception during build time:

ERROR [build.GipsProjectBuilder::49] - java.lang.UnsupportedOperationException: Currently relational expressions containing the '==' operator can not be part of boolean expressions containing operators other than '&'

[maxkratz]

I've added a test case for this: Echtzeitsysteme/gips-tests#27

[maxkratz]

This will be resolved by #145.