Fix #11414, fix #9860, fix #10434

Fix #9097

* Add conversations API

* Add web UI for conversations

* Add test for conversations API

* Add tests for ConversationAccount

* Improve web UI

* Rename ConversationAccount to AccountConversation

* Remove conversations on block and mute

* Change last_status_id to be a denormalization of status_ids

* Add optimistic locking

* Action/reducer for changing column settings takes a path and a value
instead of a javascript object

* Settings menu version and column headline version working simultaneously

* remove column headline entirely

* remove css for headlines that aren't possible now

* Remove commented out code from unfruitful attempt at this feature

* Give direct timeline its own column settings bc it doesn't have a media only option

* Fix typo in public timeline code that was preventing per-column settings from working properly

* Fix codeclimate issues

* Missing semicolons

* Use redux state to set onlyMedia, let that do the update instead of a callback. Consequently, unpinned setting works without history modification

* Unused import

* Added a timeline for Direct statuses
* Lists all Direct statuses you've sent and received
* Displayed in Getting Started
* Streaming server support for direct TL

* Changes to match other timelines in 2.0