Made sure paddle_bottom, paddle_right, etc are correct.

By subtracting one for these values, we get a width of width started at
the coordinate for the respective axis. Otherwise the length is one more
than width, which is bad. The ConcreteServerStep function still needs to
change though. It just feels buggy.
Added corner collision detection.
Made every math::vector use signed 16 bit integers.

Commented out paddleIsBesideBall function since I need to fix it and go
over it in more detail.