Add core application functionality to Qt.application in QML

This exposes some information to QML which is available on
the QCoreApplication instance.

A future change should make it possible to restrict this for use in scripting
environments (which should not have access to the QCoreApplication). That has
been left out of this change because proper support for such restrictions is
not yet in place.

Change-Id: Ica144fcfb0b42fa6df8d0cb1c7c03eb97282b489
Reviewed-by: Lars Knoll <lars.knoll@digia.com>
Reviewed-by: Kai Koehne <kai.koehne@digia.com>