Feature/css

merged again from sebaslv/related-docs and made needed changes.
@sebaslv, you can take a look as well.
Listen to the original event ("Document.Related") here, there is no extra logic in _liveDocument that is being executed before getting to this point. If you check for related this way and iterate through all of them for creating liveDocs proactively, you will also need to subscribe to notification changes. If you just check _onDocumenChange by using isRelated you don't have to listen those events for that.