[WO-592] implement webmail using socket.io
* Relax CSP to allow iframe assets to load
* Integrate socket.io proxy
* go to /# when controllers not initiated
* Add offline caching using AppCache manifest
Merge pull request #123 from whiteout-io/dev/self-hosting

[WO-592] implement webmail using socket.io
[WO-565] Improve notifications

* Introduce 2 sec timeout for sent notifications
* Notify only for new messages in the inbox
* Close pending notes when a msg is marked unread in the inbox
Focus window after clicking on notification