J2f - Add minimal topic list API for TOC

Support a TOC-only mode for the topic list, and related
refactoring to tests and topic list code:

* This is implemented by reusing data already calculated by the Pager
  (since that's all that should be needed).

  It then formats that in an alternate formatter.  There is now a base
  class, BaseTopicListFormatter, and two subclasses.

* Add tests for ViewTopicList, for the TOC formatter (however, it also
  catches some issues that are common to both TOC-only and regular).

* Fix a bug in TopicListLastUpdatedStorage.
  It was embedding a table name directly into the query.  In that position,
  MediaWiki core didn't know to auto-prefix it.  That meant that if
  wgDBprefix was set (A prefix is used in the tests  ('unittest_'),
  but this is also a user-facing setting), the query would fail.

* Changing to the testing base class to support an intentionally blank
  board, and arbitrary topic titles.

* Add back blank pagination array for empty boards (this time in parent
  class).  I removed this in 2d6d9b4 since it's overwritten for
  non-blank boards, but it is used when buildEmptyResult
  is called directly by TopicList.

* Remove obsolete constructor parameter

* Some small doc changes in TopicListQuery

* Changes max limit to use the wgFlowMaxLimit variable (note, should
  be tested in production).

This will improve performance for the TOC use case.

Change-Id: I3615817edb1500bd63dc4cbd64820fa25c943e21