Split mw.user from mediawiki.js into its own module

Split mw.user from mediawiki.js into its own module
* Split mw.user from mediawiki.js into its own module
* Except for "new Map()" to "new mw.Map()", no code was changed.
* Merged addModules call in OutputPage->addDefaultModules for "mediawiki.action.view.tablesorting" into existing call to addModules (no need for two calls, addModules takes an array)
* This also makes the mw.loader.load call at the bottom of mediawiki.js redundant (now in dependancies for mediawiki.user in Resources.php)
* Added QUnit test suite for mw.user