(bug 44665) start/stopEditing events for claimview widget
This change set implements startEditing and stopEditing events in the claimview widget which
required some refactoring in claimlistview/listview widgets.
Since there is no point in highlighting the main snak's property when adding/editing a reference,
this change set removes the highlighting as well.
- patch set 3: Fixed behavior when canceling and reverted changes of patch set 2 since
these were not implemented correctly.