* Basic memberships retrieval

* Change the way the memberships are saved in the client API database

* Retrieve single membership

* Get memberships only if the user is or has been in the room

* Check server name on room ID instead of user ID

* Save the join membership event and updates it when necessary

* Membership events retrieval + update on leave

* Implement the API on the roomserver and client API server

* Fix comments

* Remove the functions and attributes used before the new query API

* Explicitely state what we return in query

* Remove tab