Couldn't save messages because localStorage wasn't activated for xmppchat.Messages

- Previous changes broke for the use-case with Plone, where the user
  doesn't log in manually.
- These changes probably broke the manual log-in use case again, but
  the design is now a bit cleaner and it won't be too hard to fix.
- Chatboxes are now also stored in backbone.localStorage \0/

Also made some initial changes to save/fetch messages from
backbone.localStorage

Removed ControlBox model, and instead only create ChatBox models inside
ChatBoxes collection (the Controlbox is now also a ChatBox).

This enables us to use backbone.localStorage for saving open chatboxes (saving
and fetching currently not implemented).

createChatBox now doesn't return a ChatBoxView instance anymore. In the case
where a view was needed (to append a message), we create the message on the
ChatBox and let the view update via an event trigger. This is much more Backbonic ;)

Also created a Message model. This will most likely enable us to in the future also
store messages via backbone.localStorage.

Also, make sure RosterItems localstorage is user specifici

We still need a cache invalidation mechanism. Currently PEP event notifications look most promising.
http://xmpp.org/extensions/xep-0163.html
http://xmpp.org/extensions/xep-0292.html#self-pubsub

User wasn't being removed from the roster if their buddy unsubscribed.

- Also, use the browser's confirm dialog, to remove the dependency on jquery.ui

- Uses Backbone.localStorage
- Unsubscribing/removing contacts from this cache is not yet tested/implemented

- Try to clear up the confusion between presence_type (i.e type attr) and
  chat_status (i.e <show> element).
- Properly set chat status and custom status message.

- Added 'show' element
- 'busy' must be 'dnd'

Also, don't hide the controlbox in the beginning, no need to.

- Don't do an ajax call when a user wants to subscribe. We wanted to get the
  user's fullname, but this is now handled via vCards
- openChat is now only for roster items. Call showChat for controlbox and
  createChatRoom for rooms.

This time when a message is received for the first time.