Transform touch to window coords before on_touch_xxx is called. Fixes #2073. + PEP8 fix.
Merge branch 'master' of https://github.com/kivy/kivy into window-touch
Merge branch 'window-touch' of https://github.com/matham/kivy into matham-window-touch

Conflicts:
	kivy/core/window/__init__.py
Merge branch 'matham-window-touch'