FLUID-5477: Updating mediawiki to 1.19.17, removing some old unused stuff.
FLUID-5477: Removing un-used extensions
FLUID-5477: Removing more un-used extensions
FLUID-5477: Updating the Widgets extension
as per instructions found at http://www.mediawiki.org/wiki/Extension:Widgets
FLUID-5477: Updating mediawiki to 1.19.18
Merge branch 'master' into FLUID-5477