Changed aabbBroadphaseCheck to getBroadphaseBox()

All a broadphase check does is use a bigger box to do an AABB check, so
I just made a broadphase box generator instead. It'll create a
broadphase check box from a regular box and a vec2d velocity; use two of
them in aabbCheck() and you've got your broadphase check
Defined getBroadphaseBox(), fixed some namespace issues