Persist user authorization of an app

   - Add authorized_clients table, a normalized table to store authorization
     done by user for an app. Now when a user authorizes an app(grants
permission), it is remembered by swtstore and it does not ask the user to allow
the app every time.

  - Add route /users/me/authorized_apps to list all the apps authorized by
    current user, and an interface to revoke access to specific apps.

  - Structured the templates folder.
Add oauth templates; Mistakenly not added in previous commit

  - Did not add oauth view's templates previously by mistake. Adding them now.