Add initial ServiceAction implementation
Fix hashing for collections
Fix errors in basic Classifier methods
Add ext_def parsing

- Bound semantic action and parser, added ExtDefAction and made it
return values
Service now parses names correctly

- Service recognizes and applies found Id objects as name
Fix error in class definition
Add method for adding extensions

- Service meta-model can now attach `extends` clause which
  stores relation to a Classifier
Add NamedElement and Extends implementation in ServiceAction