Input handling is starting to go

Integers for key-downs.
Need to move this to a render() somewhere
Input set up to handle keypress combos

Doubt I got this right on the first go, but it's an attempt
(and it passes the "black-screen-mash-button test")
Added a little documentation

Probably unnecessary but possibly helpful.
Expanded to handle mouse/touch too

Done until I've got something to do with this input