BitmapFont, TrueTypeFont: Clean up glyphs method
BitmapFont, TrueTypeFont: Update comments
BitmapFont: Remove colorkey argument from load method

* Use pixel value at coordinate 0, 0 for colorkey (our background color)
Texture: Rename method init arg video_buffer to source
FontMetrics, FontPage, FontRow: Clean up header file deps
examples/fonts: Clean up a bit
Image: Clean up copy constructor, add err checks to init(SDL_Surface*)
MessageBox: Rename FrameStyle to Style & relocate to MessageBox class
Cursor,GrayFrame,MessageBox: Remove ui namespace