Softcatalà MediaWiki skin

This is the Softcatala mediawiki skin implemented from the mediawiki example skin, following the best practices, a companion to the
MediaWiki skinning guide available at
<https://www.mediawiki.org/wiki/Manual:Skinning>.

The code is released into public domain, which means you can freely copy it,
modify and release as your own skin without providing attribution and with
absolutely no restrictions. Remember to change the license information if you
do not intend to provide your changes on the same terms.

See <http://creativecommons.org/publicdomain/zero/1.0/> for full licensing
details.