Change status content markup to match upstream (#2923)

* Remove option to have media outside of CWs

Upstream adopted the media-in-CW design glitch-soc originally had.

* Move poll to StatusContent

* Refactor status media icons

* Rename `forceFilter` to `showDespiteFilter` for consistency with upstream

* Change media and status content markup to match upstream's

* Add mention placeholders back

app/javascript/flavours/glitch/reducers/local_settings.js

@@ -23,7 +23,6 @@ const initialState = ImmutableMap({
   rewrite_mentions: 'no',
   content_warnings : ImmutableMap({
     filter       : null,
-    media_outside: false,
     shared_state : false,
   }),
   media     : ImmutableMap({