Made window orientation API more flexible.

Previously we only had QWindow::setOrientation() which was a hint about
the orientation the window's contents were rendered in.

However, it's necessary to separate between the orientation
corresponding to the window buffer layout and orientation of the
contents. A game for example might typically want to use a landscape
buffer even on a portrait device. Thus, we replace
QWindow::orientation() with QWindow::reportContentOrientationChange() and
QWindow::requestWindowOrientation().

Change-Id: I1f07362192daf36c45519cb05b43ac352f1945b5
Reviewed-by: Lars Knoll <lars.knoll@nokia.com>