Implement better version of the fps counter

This uses the frameSwapped signal of the parent window of a QQuickItem instead of relying
on the speed of an animating image.

Signed-off-by: Simon Busch <morphis@gravedo.de>
Implement simple screenshot component

Signed-off-by: Simon Busch <morphis@gravedo.de>
Merge pull request #29 from webOS-ports/morphis/fps-and-screenshooter

New FPS counter and component to make screenshots