* Offset updates take place using TransactionWriter
* Refactor TransactionWriter in current state server
* Refactor TransactionWriter in federation sender
* Refactor TransactionWriter in key server
* Refactor TransactionWriter in media API
* Refactor TransactionWriter in server key API
* Refactor TransactionWriter in sync API
* Refactor TransactionWriter in user API
* Fix deadlocking Sync API tests
* Un-deadlock device database
* Fix appservice API
* Rename TransactionWriters to Writers
* Move writers up a layer in sync API
* Document sqlutil.Writer interface
* Add note to Writer documentation
* 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
* Initial persistence of blacklists
* Move statistics folder
* Make MaxFederationRetries configurable
* Set lower failure thresholds for Yggdrasil demos
* Still write events into database for blacklisted hosts (they can be tidied up later)
* Review comments
* Deduplicate FS database, add some EDU persistence groundwork
* Extend TransactionWriter to use optional existing transaction, use that for FS SQLite database writes
* Fix build due to bad keyserver import
* Working EDU persistence
* gocyclo, unsurprisingly
* Remove unused
* Update copyright notices
