[DIC]: @var type-hinting, /dic/README.mediawiki -> /dic/README.md

+ README.mediawiki doesn't show source examples appropriately therefore
move to md format
+ Add some @var
+ Add MockUpdateObserver test for \SMW\LinksUpdateConstructed now
that the \SMW\ParserData object is fully resolved by the DIC

Change-Id: I8a1a9ad6af11d677c50721ae3af74610da9d92da