Cleanup Of Image Formats
Made sure all sprite and background saving and loading work properly with
BMP and PNG, image formats uses RGBA at all times, can be expanded later
as well as add support for APNG, JPEG, GIF, and other formats. Please
merge.
Adding comment for background_save and sprite_save not working with
non power of two textures.
Merge pull request #486 from RobertBColton/master

Cleanup of Image Formats