Fix LTL ouput for empty group definitions
Two safeties of the same spec type with a connective are now considered a safety
Fix LTL translation of sentnces over empty groups and one-item groups, enable multiple _add_to actions in a single sentence
remove debugging print statement and revert change to path to grammar file
Merge branch 'nltkParser' of github.com:LTLMoP/LTLMoP into openworld