WIP: Add streaming for public and external.

Things we need before this can go in:

• Proper connection problem management with:
  • Re-establish lost connections, if possible with closing holes (fetching normally once)
  • Switching to normal REST if the websocket can't be established. Switching back to streaming if it comes up again

A second problem is that the Mastodon API (that this is based of) doesn't give you the relationship information for the user (if they are following you and so on). So if a user comes in through this mechanism, it will not have this information available. I'm not sure if the profile pages (both in-line in statuses and the page itself) will refetch users on view, but they should do this to account for this problem.