Add Support for Non-60Hz Screens

[hammerill]

I just bought a 144hz monitor and tried to launch Sand-Box2D. It ended up being unplayable because of misaligned framerate.

[hammerill]

It can be fixed easily by turning on the speed correction, but I want to be able to run the game at any framerate possible.

[hammerill]

Also it launches not at native monitor resolution (monitor is 1080p, game is 864p).