Start working on tightening our control of the Navigation context

Currently breaks posting.

TODO:
* Fix style switching from NSFW to SFW (SFW to NSFW works)
  - It is worth noting this used to work.
* Fix post form not updating its currently selected thread.
* Fix navigation between threads in different boards (same boards
  works? Maybe?)
* Handle race conditions due to pop states.
  - I'm having a lot of trouble wrapping my mind around this one.
    Mostly due to the fact that I have no idea where to begin with
    it. But this isn't a big issue unless you pop state multiple
    times within seconds.

    I just need some exceptions when we try to disconnect features
    that haven't even finished connecting due to threads not being
    available yet.

Most of the early issues, like double-backlinks, incorrect
thumbnails, etc, have been fixed, I think. Or at least I'm no
longer running into them all the time.