[DB MIGRATION REQ'D] Implement and Enable DB-Backed Sessions

I think just close the other request.  Needed to merge in your fix and some new fixes.

Creates SessionDAO Interface and MySQL implementation
Creates session table
Adds SessionCache::init() to start sessions and set handlers
Modifies controllers to make use of this
Moved date_default_timezone_set($config->getValue('timezone')); before SessionCache::init call.
   The DateTime construct error was happening because in ThinkUpController, SessionCache::init was being called in ``__construct``, before ``initializeApp``` is called in ``go``. The default timezone is set in ``initializeApp``.

Fixes for failing tests from Session Changes
  Handle new tables in installer test
  Handle session already startin in other tests in Controller test.
  Fix wrong table count in mysql install dao test.

Fixes for tests with database sessions.
  Set a TU_MODE in setmode, check for that cookie
  in the various places needed.


References #962