mediawiki: make a new Bitraf skin based on one of the default skins that comes with Mediawiki

[tingox]

The current Bitraf skin is from a very old version of Mediawiki, and is horribly broken. Updating it so it works with the current version of Mediawiki is very hard.

Suggestion: use one of the current skins delivered with Mediawiki today (MonoBook, Timeless, Vector) as base, and create a new Bitraf skin from that. If we limit the changes to only the things we "need" it will be easier to maintain as well.

Suggested minimum changes:

• Bitraf colors
• Bitraf logo