Move user cookie functions into user model.
Add Autologin model.

This model is intended to be auto-loaded into CodeIgniter, and it will look
for the persistent user cookie and automatically establish a new session
as long as the user is valid and their access token is still valid.
Fix auto-login logic around existing session.
Translate register page and OAuth errors.

This also refactors translations, in general, through an auto-loaded
translate helper that defines the function tr() similar to Qt to make
invoking translations short and convenient.
Add user view page.

This also adds the ability to use templated translation strings and pass
data into the tr() function for the template parser.
Add ability to edit user data.

Anyone can edit their comment and language. Only the bureucrats can
edit roles or other user's data.