Stamp: Format fix
Font: Add GetKerning method
Add ScaleFactor to various text data structures
Stamp: Add Kern method

Pass in a value to advance current x-position by, for kerning
test/font: Kern the text
GlyphMap: Extract now fills a Stamp

Also added a bunch of get/set interfaces to the Stamp class.
test/font: Clean up test
Stamp: Bind 0-name after setting texcoords
Texture: Data members now protected
CompositeTexture: Partial Create implementation
CompositeTexture: Take out of gdk namespace
CompositeTexture: Create implementation
Add compositetexture test
CompositeTexture: Clean up memory and end log block where needed
CompositeTexture: Tweak how texture params are set
Decode: DecodeImageFile implementation
Add simple UI button art
CompositeTexture: Fix corner data copy implementation
Decode: Log error in DecodeImageFile
Decode: DecodeImageFile loads through IO callbacks

AWESOME feature in stb_image that lets use decode images in tandem with
PhysicsFS without having to load the entire contents of the file into a
huge buffer and pass that to stb_image. Through io callback loads,
stb_image requests chunks of memory (or to skip through). This way we
don't need a FILE pointer or to buffer the whole file. Sweet!.