Adding a test application supporting output to a QWidget

This test application "testRenderingServer" is able to start a
Wayland server and uses a QWidget to render the "scene". It manages
ShellSurfaces and renders them on the QWidget in a very static way.
Furthermore input events (key, pointer, wheel) are forwarded to the
top most Surface.

This test server is able to support kwin_wayland as a client, but
weston's test application in latest release fail due to missing
xdg_shell support.