Add mouse support and better input broadcasting

Fixes https://github.com/comscript/Sosu/issues/3 (optimize bindEntity())
Fixes https://github.com/comscript/Sosu/issues/4 (add mouse support)
Fixes https://github.com/comscript/Sosu/issues/5 (pass pressed/released to input handlers)
Fixes https://github.com/comscript/Sosu/issues/6 (move input handling from Sosu to World)