Add getVCard method (will be usefull for caching later)
Replace another server call with VCard.

This time when a message is received for the first time.
Various fixes, see below:

- 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.