Service Containers

Some clean up of the internals of circuit to reduce number of attributes added to the Request. All modifiable information about the controller (class, method, args) now sit in a simple value object in the request attributes - $request->attributes->get('controller').

Also, instead of passing arbitrary controller arguments, have standardised on PSR-11 containers and there for have changed the $router->setControllerArguments([$arg, $arg2, ...]) function to $router->setServiceContainer($container)