removed leftover of an debuging session in FirstPostProcessing
Reworked the initial initialisation of an example:
   do it after the viewport size is set and not before( e.g. caused a crash when FirstPostProcessing was set as initial example)
Bugfix: when toggling fullscreen mode from fullscreen to window then the content is still shown as in fullscreen but no updates are visible
without glPushAttrib(GL_ALL_ATTRIB_BITS) and a corresponding glPopAttrib it seems that unrimp changes some attrib bits which confuses qml scenegraph
only use a cyclic update timer, when the examples wants it