SpecialUnwatchedpages: Ajaxify watch links

Add user friendly handling to watch pages from Special:UnwatchedPages
using ajax. Emits a notification message upon completion of the action
and strikes through the list item.

Bug: 17367
Change-Id: Ie32cc54abb6f888a433f7f18ef5ad747a80d7187
Merge "SpecialUnwatchedpages: Ajaxify watch links"