TablePager: Modernize style loading

* Create a CSS module for pager styling (table and navigation),
  pulling in existing styles for shared.css. Load it on all pages
  where the pager itself is shown.
* Build a ParserOutput object encapsulating the return HTML and
  required modules, rather than only providing the HTML. Added some
  hacks for backwards-compatibility with old-style calls and
  soft-deprecated them (there are many usages in extensions).

Other cleanup:
* Remove styles in oldshared.css, they were all overwritten by
  shared.css or by styles for .mw-datatable.
* Remove inline styles where possible, explain them where impossible.
* On SpecialListFiles, display navigation bar above the table as well
  as below (this seems to be the convention for other pages).

Change-Id: Iae976f854b96b5c61691918787c4dff7db089c28