Move Arc creation into ArcCreator's

* Add tests
Add property listeners for dragging arc
Add change listeners for transition

* Cant work out why setting tooltip in ctr doesnt display transition
  just call repaint in change listener until fixed
Fix bug in TransitionEditor, now can set priorities and exit
Add name label change listener to connectable
Move adding PetriNetComponents out to PetriNetChangeListener
Remove PetriNetView from creation process
Add cancellation handler for temp arc view
Remove IObserver and IObservable
Fix up some failing unit tests