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.
Add word boundaries to the style switcher regex
Fix updating the context of threads and index
Revert "Fix updating the context of threads and index"

This reverts commit e7b1c52dbf9f25aec32bea64c712ee4075f7ef6f.
The good parts.
Merge branch 'v3'

Conflicts:
	LICENSE
	builds/appchan-x.user.js
	builds/crx/script.js
	src/General/Navigate.coffee
	src/Posting/QR.coffee