* 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

* Storage functions for invite events

* Add table for tracking membership state

* More stuff

* More stuff

* Use utility methods from gomatrixserverlib, rather than reimplementing them

* More stuff

* Return string rather than pointer to string

* Update gomatrixserverlib

* Use HTTP API for roomserver input.

* Use synchronous HTTP API for writing events to the roomserver

* Remove unused config for kafka topic

* Add new output types to roomserver for invites

* Write membership updates

* Separate filtering from pairing up changes in membershipChanges

* Fix SQL

* Fix SQL

* Namespace the tables

* Fix SQL

* Use clearer names for some of the variables

* Rename senderID for consistency

* Restructure update membership

* Comments

* More comment

* Fix SQL

* More comments

* Assign state keys inside the transaction

* Comment on the purpose of the latestEventsUpdater

* Comment on the purpose of updateMembership

* Remove duplicate fields from stateChange

* Attempt to rewrite comment in 'english'

* More comments

* Fix comment

* Comment

* more comments