Reasonably implement love.graphics API

[darkf]

http://love2d.org/wiki/love.graphics

Getters like getColor (which will probably need a default and then use that), graphics styles and blend modes, rotations, transformations, etc.

Blend modes might be an issue because different versions of browsers handle them differently or straight up don't implement them. I guess we could just not handle this at all and let browsers decide to implement it. If we were in WebGL we could provide a shader for it, but alas. :P

A lot of it is really straightforward and shouldn't pose a problem. We'll probably omit pixel effects because they're slow with the canvas (requiring locking the canvas, iterating over every pixel and calculating a new value, then writing it back and unlocking it.)