[mediawiki.action.watch.ajax.js] Rewrite using mw.Api and fixes bug 27146

[mediawiki.action.watch.ajax.js] Rewrite using mw.Api and fixes bug 27146
* Use mw.Api and new it's new .watch() as of r107350
* No longer get title from url, use wgPageName instead
* No longer simple queryParam check for action in url,
  now supports wgActionPaths as well.
* Simplification and speed up (less back and forth between
functions and jQuery-ism). Previously it had $(..) with several
.add() calls. Now doing one call.
* Uses mw.util.tooltipAccessKeyRegexp instead of local regex
* Uses jQuery.fn.text instead of jQuery.fn.html for link text message

* Should fix bug 27146 (previously a failed attempt in r82498)
* Previousy worked on in r88527, r88511, r78150, r78147

* minor whitespace/comment fix in mediawiki.util.js/mediawiki.page.startup.js