Add defaultSurfaceFormat to QQuickWindow

This static function can be used to set a surface format that is
then picked up by all QQuickWindows, including the ones instantiated
from QML.

This introduces the ability to request higher OpenGL versions, core
profile and other options also for windows that are created from QML
via the ApplicationWindow element in Quick Controls applications.

[ChangeLog] Added QQuickWindow::setDefaultSurfaceFormat() to
set a surface format that applies to all Quick windows,
including the ones created from QML. The OpenGL shading language
version is now exposed to QML too in order to allow components
to provide the correct shader source so shader effect items.

Task-number: QTBUG-36392
Change-Id: I75a4718243d835894461f7ee0b4a383988840f9b
Reviewed-by: Gunnar Sletta <gunnar.sletta@jollamobile.com>