Softdeleteable related updates

closes #739
closes #554 

Handles softdeleted slug uniqueness checks implicitly. Here is some minnor BC break if `addManagedFilter($name)` was used explicitly for sluggable.

### Points of improvement

- [x] make filter ignorance available at base listener class, to share common behavior between listeners
- [x] implicitly manage softdeleteable filter for sluggable listener without any user intervention.
- [x] update tree **lft** **rgt** values, when nodes were softdeleted
- [ ] handle translations related to an entity, do not remove them