Finished powerups, changed keys.

Powerups (beam, double) now use their correct, individual counters
(doomBeamNum and doubleShotNum).
New keybindings:

b: beam
v: double

o: bomb (deprecated)
p: rapid fire (deprecated)

M also still activates rapid fire.

Some debug test ability was removed (other weapons no longer available by
cycling 'f')
Merged Alex and Fintan's powerup + control code

Powerup handling uses Fintan code
Control scheme includes both num keys + cv
Natural powerup acquisition uses Alex's code (double every boss, beam
every 3)

Conflicts:
	code.js