Mautrix

* Fixed notification disabler breaking when not using double puppeting.

* Added `NotificationDisabler` utility class for easily disabling notifications
while a bridge backfills messages.

* Added support for automatically calling `ensure_registered` if `whoami` says
the bridge bot is not registered in `Bridge.wait_for_connection`.

* Moved initializing end-to-bridge encryption to before other startup actions.

* Added extensible enum class ([14]).
* Added some asyncpg utilities.
* Added basic config validation support to disallow default values.
* Added matrix-nio based end-to-bridge encryption helper for bridges.
* Added option to use TLS for appservice listener.
* Added support for `Authorization` header from homeserver in appservice
transaction handler.
* Added option to override appservice transaction handling method.
* Split `Bridge` initialization class into a more abstract `Program`.
* Split config loading.

[14]: https://github.com/mautrix/python/issues/14

* Added option to add custom arguments for programs based on the `Bridge` class.
* Added method for stopping a `Bridge`.
* Made `Obj` picklable.