* 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
