QtMir Desktop Mode behavior adaptations
requested to merge personal/fredldotme/desktop-development-improvements into personal/mariogrip/desktop-development
Multiple changes regarding the use of Lomiri and QtMir in a desktop use-case, with windows popping in and out of existance and having resources removed adequately. Also fixes up some positioning and resizing of surfaces and goes at fixing some stability issues with regards to subsurface usage in the Qt Scene Graph renderer.