Keyboard support: game controller not required anymore

Sorry for taking so long to add such an essential functionality. Problem is, it took me some time to realize many players didn't have (or simply didn't want to use) a Xbox-compatible controller to play the game. So, here it is: [b]WASD or arrow keys:[/b] movement / menu navigation [b]Spacebar:[/b] fire / OK [b]M or ESC:[/b] boost / Cancel [b]< and >:[/b] change weapon