adding a new interface for providers willing to register event listeners
moved Swiftmailer finish call to a proper listener
emptied the boot() method of the remember me service provider
moved fake routes for the security service provider to a connect() method (with auto-registration)
moved the provider interfaces under Silex\Api
added BootableProviderInterface
changed type-hint to Pimple whenever possible
moved classes so that Silex\Provider can be used as a sub-tree split independently of eveything else