Assign web application launch point url directly

Signed-off-by: Simon Busch <morphis@gravedo.de>
Rework stagePreparing/stageReady implementation

We now really show the window once the application has called stageReady or a timeout
occured. As long as none of both happens the window stays hidden.

Signed-off-by: Simon Busch <morphis@gravedo.de>