Fix #4485

* Add keyword filtering

    GET|POST       /api/v1/filters
    GET|PUT|DELETE /api/v1/filters/:id

- Irreversible filters can drop toots from home or notifications
- Other filters can hide toots through the client app
- Filters use a phrase valid in particular contexts, expiration

* Make sure expired filters don't get applied client-side

* Add missing API methods

* Remove "regex filter" from column settings

* Add tests

* Add test for FeedManager

* Add CustomFilter test

* Add UI for managing filters

* Add streaming API event to allow syncing filters

* Fix tests

* 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