Add support for using the router without the full framework

[davidbyoung]

The documentation discusses how to use the router library without the full framework. However, there is still boilerplate that needs to be written to use it. Ideally, we have a way of using the router (along with attributes like #[QueryString]) to do some simple routing to a POPO controller.

Todo:

• [ ] What HTTP library do we use? Aphiria's or PSR?