[sample] Replace PNG_512x512_318Kb_BBB.png with ryb-100x100.png

- This image is only referenced by Screen Orientation sample,
  which makes a colorful view.
- Improve Screen Orientation sample code and format.
- Remove unnecessary COPYING files.
Merge pull request #829 from zqzhang/PNG_512x512_318Kb_BBB.png

[sample] Replace PNG_512x512_318Kb_BBB.png with ryb-100x100.png