Direct messages column (#4514)

* 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

app/javascript/mastodon/reducers/settings.js

@@ -58,6 +58,12 @@ const initialState = ImmutableMap({
       body: '',
     }),
   }),
+
+  direct: ImmutableMap({
+    regex: ImmutableMap({
+      body: '',
+    }),
+  }),
 });
 
 const defaultColumns = fromJS([