Put everything shared in a Container class
Fix missing auth URL in index.twig
Refactor some of the adnlib, change callback URLs

This also adds a centralized method of accessing params via the
Container class (i.e. Container::getParam($key, $default)) so we can use
that instead of the `global` keyword (which is ugly and error prone).
Add /signin.php, /signout.php endpoints

Also sure we're using the new session endpoints in the auth_menu
partials
Add tags (phptags) target to RoboFile
Require settings.php in the bootstrap file
Move the first mention tool to Twig
Fix missing auth_url in unauth_message.twig
Add almost-working follow comparison tool

The only thing missing is the actual follow logic