general clean up. s/alpha/beta/g. add intelfx's AUR package for Arch. s/the homeserver/Synapse/g. move installation & running sections closer together.

Postgres

Client / Server Auth Refactor

Invite power level

Fix for SYN-266

Observer and locks

`create_observer` takes a deferred and create a new deferred that
*observers* the original deferred. Any callbacks added to the observing
deferred will *not* affect the origin deferred.

Shuffle operations so that locking upsert happens last in the txn. This ensures the lock is held for the least amount of time possible.