Use single class change to trigger computing state #2761
Remove ability to collapse filter hierarchy #2761

This was not used much, and the same effect can be obtained by
carefully selecting the filters we are interested in
Could not save questionnaire from menu #2761

Also almost finish refactoring in service
Avoid useless concatenation #2761
Could not always delete answers #2761
Create custom directive for filter value #2761

Custom code allow us to avoid $watch() as much as possible and rely
instead on well timed events and custom on-the-fly behavior
Use custom directive instead of ng-class #2761

This reduce even further the need to $watch()