- class order fixes
- static methods (creators) at the beginning
- then constructors / destructors
- then init
- more `const` fixes
- adds some const getters
- some getters have 2 versions: `const` and no-const version
- renamed CocosDenshion::sharedEngine -> getInstance()
... instead of sharedXXX / purgeXXX.
They are more C++ friendly, and also easier to remember.
common files + Mac files + iOS files + tests/samples files were updated.
The old methods are deprecated now.