Implement "relevant" title and user in the skin system and update undelete, log,...

Implement "relevant" title and user in the skin system and update undelete, log, contributions, blockip, and movepage to use it.
A "Relevant" is used by the skin to determine what title to display tabs for. This setting allows pages like Special:MovePage (which is linked to from the tabs themselves) to retain the tabs specific to the page relevant to it when switching to the special page.
Similaly a "Relevant" user is used by the skin to display things in the toolbox which would usually only be displayed on the user's userpage and talkpage, pages like Special:Contributions which are linked to by the toolbox can use this to retain the toolbox links when switching between the user pages and these special pages.