Wiki footer change

• download the needed picture (e.g. from http://i.creativecommons.org/l/by-nc-sa/3.0/88x31.png).
• save it to /usr/share/mediawiki1.7/skins/common/images/; if so desired, rename it (we did: to by-nc-sa_88x31.png); remember to set the owner to root:root.
• change /var/lib/mediawiki1.7/LocalSettings.php to include the following line:
  

  $wgRightsIcon = "https://oberon.saruman.biz/wiki/skins/common/images/by-nc-sa_88x31.png";

That's it!