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

app/javascript/mastodon/locales/defaultMessages.json

@@ -755,6 +755,19 @@
     ],
     "path": "app/javascript/mastodon/features/compose/index.json"
   },
+  {
+    "descriptors": [
+      {
+        "defaultMessage": "Direct messages",
+        "id": "column.direct"
+      },
+      {
+        "defaultMessage": "You don't have any direct messages yet. When you send or receive one, it will show up here.",
+        "id": "empty_column.direct"
+      }
+    ],
+    "path": "app/javascript/mastodon/features/direct_timeline/index.json"
+  },
   {
     "descriptors": [
       {
@@ -816,6 +829,10 @@
         "defaultMessage": "Local timeline",
         "id": "navigation_bar.community_timeline"
       },
+      {
+        "defaultMessage": "Direct messages",
+        "id": "navigation_bar.direct"
+      },
       {
         "defaultMessage": "Preferences",
         "id": "navigation_bar.preferences"