install the gnome-control-center so users can change settings in the gnome shell session

git-svn-id: https://rebeccablackos.svn.sourceforge.net/svnroot/rebeccablackos@3012 56e3d1a8-0179-4092-b3e2-9fbbcda0c0a9
work around and use the unity control panel in place of thee gnome control panel for gnome-shell sessions, as it actually has icons

git-svn-id: https://rebeccablackos.svn.sourceforge.net/svnroot/rebeccablackos@3013 56e3d1a8-0179-4092-b3e2-9fbbcda0c0a9