Rotation of Window simulating Android on win, linux and macosx

Update modules/keybinding.py
Merge branch 'master' of https://github.com/kivy/kivy into rotateOnLinux
Undoes the strategy of the commit 646aabd;
that commit replaces a feature, this adds one.

Brief update of the module documentation.

Bugfix for F11 key binding.
Bugfix for F12 key binding.
Merge branch 'master' of https://github.com/kivy/kivy into rotateOnLinux
Merge pull request #1137 from alexandre-mbm/rotateOnLinux

Rotate window on linux