* Add InputDeviceListUpdate
* Unbreak unit tests
* Process inbound device list updates from federation
- Persist the keys in the keyserver and produce key changes
- Does not currently fetch keys from the remote server if the prev IDs are missing
* Linting
* Add QueryDeviceMessages to serve up device keys and stream IDs
* Consume key change events in fedsender
Don't yet send them to destinations as we haven't worked them out yet
* Send device list updates to all required servers
* Glue it all together
Kegsay