New mediawiki.page modules

New mediawiki.page modules

First step towards cleaning up mw.util.init and removing bugus dependancies on mediawiki.util which are just added there in order to load them on every page and do something on-load.

Introducing mediawiki.page.startup (in the head) and mediawiki.page.ready (on the bottom)

Moved the following to them:
* document.ready from jquery.cient
 -- Shouldn't have been in the plugin itself in the first place
* jquery.placeholder
* jquery.makeCollapsible
* mediawiki.action.view.tablesorting
* jquery.checkboxShiftClick

(This also solves part of bug 26799)