One state monolithic invariant generation without communication.
Numeral constants can be negative in Lustre input

Numerals are always positive, negative numerals have a unary minus
applied to their absolute values. Allow negative numerals as constants
in Lustre input.
Merge pull request #163 from chsticksel/develop

Numeral constants can be negative in Lustre input
Changed graph logging, reactivated two state inv gen.
Merge remote-tracking branch 'upstream/inv-gen' into invGen
Instantiation of terms in the trans sys hierarchy.
Term instantiation at top level in trans sys.
Modular invariant generation with instantiation.
Invgen working, need to do subsys candidate generation.
Bug fix in transsys (comparison).
Invgen uses invariants in lsd at all levels.
Invgen uses invariants in lsd at all levels.
InvGen uses invariants received by events.
Optimization in transSys and invGenGraph.
Heuristic candidate term generation for int variables.
Check termination in base step and invgen.
Check termination in base step and invgen.
Merge remote-tracking branch 'upstream/develop' into invGen
New invgen rules, termination check in lsd.
bug fix in lsd