Keyword/phrase filtering (#7905)

* 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

app/javascript/mastodon/reducers/index.js

@@ -26,6 +26,7 @@ import height_cache from './height_cache';
 import custom_emojis from './custom_emojis';
 import lists from './lists';
 import listEditor from './list_editor';
+import filters from './filters';
 
 const reducers = {
   dropdown_menu,
@@ -55,6 +56,7 @@ const reducers = {
   custom_emojis,
   lists,
   listEditor,
+  filters,
 };
 
 export default combineReducers(reducers);