Using the mw alias for mediaWiki in core. Saves bandwidth and makes sense (there...

Using the mw alias for mediaWiki in core. Saves bandwidth and makes sense (there's no point in a wrapper function for ($,mw) if we use jQuery and mediaWiki inside of it).

TODO: Since the alias is globally available from the start, the 'mw' argument in the wrapper is redundant, so that should be removed at some point as well.