ScalableGame, Cleanup/formating, small fixes

- Move everything from default package to 'adhoffman.swiftshadows'
package

- Use ScalableGame as wrapper around the game, will keep the aspectRatio
and handle all the input scaling automatically.

- Clean redundant return value: 'if (x == null) return x' to 'return x'
in
'Level.java'

- Make enum constants UPPERCASE to stick with the java convention

- Rename Graphics objects 'gr' to 'g', convention in game development

- Add 'STATE_PLAYING' constant to 'Constant.java' and
'PlayingState.getId()'

- Format all files

- Remove windows natives from 'lib' folder, added various operating
system natives to 'lib/native' folder (check your project to add the
correct files)