Add command line options to be able to set the QCoreApplication attributes
that influence Open GL context creation and add a status label at the
bottom that displays it besides the QT_OPENGL environment variable.

Task-number: QTBUG-52693
Change-Id: Id9793292596e0feb3da5220fde2e5b2e495f87ff
Reviewed-by: Laszlo Agocs <laszlo.agocs@theqtcompany.com>