* Stored base offsets and vertices in sprite structure
* Calculated the average of vertices in polygon and chain shapes and used that as center
* Applied offsets to drawSprites()
* Fixed bug that would cause the renderer for sprites to be corrupted on when the sprite vector is resized
* Changed deleted_sprites variable to deleted_animation in sprite object
* Changed sprite pointer vector to sprite id vector in canvas object
* Changed the value stored in Fixture UserData pointer to sprite id rather than sprite pointer because pointer would change on resize anyway
Finished documentation on sprite physics and joints
Fixed some bugs in sprite physics
Added safety checks for joint types
Added code to free up joints when a canvas is destroyed
* Rewrote the actor animation system to work like sprites
* Renamed a few functions
* Added DeleteSpriteAnimation() and the delete queue to sprites
* Removed transitions for the time being (they don't seem to work in irrlicht right now
* Added PreUpdate() function
* Added documentation for name changes and new functions
* Added collision callback
* Set sprite density to 1 by default
* Added default frame value of 0 on frame resize
* Changed defaults for sprite fixture
* Made changes to some of the animation functions parameters
