Adds the ability to connect/login to an account via the settings and
auto-configuration dialogs. Checks registered Auth objects, and if the
Auth object matches the currently selected service in the settings
window or auto-configuration dialog, will display "connect account"
buttons for the user to be able to click (which are optional, they can
still use stream keys if they'd prefer).
Makes it so that services can have custom handling on a per-service
basis. The bottom part of the service pane is now a stacked widget
which can now be customized for different types of services
(particularly OAuth services).