Inform the user when weston is sharing itself with RDP

git-svn-id: https://rebeccablackos.svn.sourceforge.net/svnroot/rebeccablackos@3101 56e3d1a8-0179-4092-b3e2-9fbbcda0c0a9
Try to support making closing the dialog kill the RDP session

git-svn-id: https://rebeccablackos.svn.sourceforge.net/svnroot/rebeccablackos@3102 56e3d1a8-0179-4092-b3e2-9fbbcda0c0a9
Users can now terminate the shared RDP session by closing the dialog, so inform the user.
Make westonrdpcaller use rdpdialog, as the zenity strings are now the same

git-svn-id: https://rebeccablackos.svn.sourceforge.net/svnroot/rebeccablackos@3103 56e3d1a8-0179-4092-b3e2-9fbbcda0c0a9