New multi app supporting sidebar navigation

Summary:
This diff changes the sidebar navigation, fixing a bunch of issues:
It will be possible to quickly switch again between the same plugins in multiple apps
No need to expand-and-check the app dropdown until the app is connected
No need for ugly fallback selections if some app connects faster than another one

Reviewed By: nikoant

Differential Revision: D19272701

fbshipit-source-id: 10f5fab42391014ef4a4a4c91c529d93f8bfb125

static/icons.json

@@ -81,8 +81,9 @@
     16
   ],
   "chevron-up": [
-    8,
-    12
+    12,
+    16,
+    8
   ],
   "compose": [
     12