Import QTDIR using a property sheet with a relative directory

For compatibility with existing build processes, import QTDIR using a property sheet.  If QPubNub.vcxproj changes upstream, Qt.props will have to be added to the updated vcxproj.
If we need to reference our own files in the Qt.props anyways... why don't we link here to our own Qt.props file? /Desktop/Source/Qt4.props