Hotfix for Super Power Frenzy

I've recently fixed a few ~~cataclysmic~~ minor bugs and also added some alternative control options for players with slightly different preferences, as well as making a minor optimisation which may help the game run smoother.
Full patch notes!
Tweaks: - Added left stick support for XBox One / 360 controller as an alternative to aiming - Added A button support for XBox One / 360 controller as an alternative to shooting
Optimisations: - Optimised player gun code
Bug fixes: - Fixed planetoids displaying incorrect power per second value - Fixed item drops incrementing player kill count - Fixed fire button not working on Mac
Link to game entry: https://ldjam.com/events/ludum-dare/39/super-power-frenzy