Rebrand kubuntu-settings

Here's a start. The changes so far:

* The "About System" in System Settings uses the Trisquel logo, links to the Trisquel website (https://trisquel.info), and says "Triskel GNU/Linux 7.0" rather than "Kubuntu 7.0". I will have to add the copyright for the Trisquel logo in the copyright file.

* Change the default IRC channel for Konversation to #trisquel on chat.freenode.net (port 6997 for SSL)

* Change the homepage for Konqueror from the Kubuntu website to the Trisquel website, and change the Kubuntu bookmark to Trisquel in rekonq.

The file didn't get attached properly, as usually (in the issues section), but I found that you can get it at the URL https://trisquel.info/files/issues/kubuntu-settings_14.04ubuntu15.tar_.xz. (The mime-type isn't correct it seems)