[themes] Tango iconset: Default for drupal, is NOT GPL.

Hello,

I only realised this today, but our guidelines speak about using tango as default iconset. We abide these rules very well, in the contribs the mayority if icons are indeed tango icons.

But they are not GPL, nor can they be distributed as such. We should address this, and possibly choose another default iconset, or else change our licencing policy.

«The Tango icons are licensed under the Creative Commons Attribution Share-Alike license. The palette is public domain, it can be used and distributed freely. Developers, feel free to ship it along with your application. The icon naming utilities are licensed under the GPL» --- from http://tango-project.org/Tango_Desktop_Project

Bèr