Merge pull request #181 from AdrienChampion/feature_timeout-tag

Added easily greppable tags for timeout, error, and interruption.
Merge remote-tracking branch 'upstream/develop' into invGen-no-explicit
More explicit no_trans_subterms option.
Fixed conflicts in flags.
Backward unrolling, changed many thing. fixes #184
Bugfix in step, not ignoring invariants now.
Subsystem candidate term extraction.
Merge pull request #185 from AdrienChampion/invGen-no-explicit

Invariant generation, one state and two state