Add USB support

[TomAwezome]

USB stack with support for keyboard and mouse would resolve most or all 'unsupported' keyboard/mouse bugs on modern hardware, as it can replace relying on legacy BIOS PS/2 USB emulation. Would likely properly resolve #70.

[slendidev]

However, if USB will be used for input, it will probably be best to not mess with the existing PS/2 drivers, but build on top of them.

[TomAwezome]

Sounds good