Fix #9031
Fix #7913

* 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

* Hide section headline for timelines in production

* comment out

ref https://tc39.github.io/proposal-decorators/

* Add regex filter on the community timeline and the public timeline

* correcting

* Adjust the height of header buttons

* Remove trailing spaces

* Remove trailing spaces

* Solve some code duplication

* reset the state of the locale files in app/javascript/mastodon/locales

* adjust to upstream

* adjust to upstream

* change keys of locale settings