A Bunch Tell is now Musing Studio.

Now when we check for the user at certain times and find that the user
doesn't exist in the database, we log them out and send them back to
the home page.

This adds beginning email subscription functionality, with only MySQL support,
Mailgun support, and incomplete support for private instances. It includes
database changes, so run:

    writefreely db migrate

to use this feature.

Ref T856

This fixes logging in when developing on newer versions of Chrome.

- Adds a new interface, Apper, that enables loading and persisting
  instance-level data in new ways
- Converts some initialization funcs to methods
- Exports funcs and methods needed for intialization
- In general, moves a ton of stuff around

Overall, this should maintain all existing functionality, but with the
ability to now better manage a WF instance.

Ref T613

Ref T613