Implemented non-continuos "dirty" rendering for iOS.

This pull requests adds fully working non-continuos rendering on the iOS backend.
Touch and key events automatically trigger rendering requests like on the other backends.

Tested with the DirtyRenderingTest: https://github.com/libgdx/libgdx/blob/master/tests/gdx-tests/src/com/badlogic/gdx/tests/DirtyRenderingTest.java


P.S. I've removed one unnecessary hack from IOSInput and used the libgdx code formatter template on the changed classes.