[WIP] Notifications

* Implemented localStorage based storage mechanism for notifications
* Improved init mechanism
* Added notification badge
* Added notification flyout based on OO.ui.PopupWidget
* Added assets for button template and OPT-IN gadget
* Now using marker for base page insertion
* Built own message dialog to have anchor tags displayed

TODO
* Find reason for strange DB errors in API calls with "\n" in parameter
* Fix popup displacement

Change-Id: I525195eac98ff7addd6f47546f40d50daf51d707