(bug 48376) Customise Wikimania team wiki logo

This patch changes $wgLogo for the Wikimania team wiki from
a non-public version (that I have never even seen :) into
a customised and losslessly compressed logo available on
Commons per bug request.

Obviously, the file page on Commons is fully protected
against uploads and moves.

I'm also moving the logo definition for the Spanish Wikivoyage
higher into the file to match the usual alphabetical sorting.

Bug: 48376
Change-Id: I524ea13c66391d35b7e1def04c29a0e1908259ad