Add Sorting to topic list based on last updated timestamp

The solution is based on what we discussed in the estimation meeting.
This is probably not the most optimal solution since the ordering list
is in one table while the ordering field is in another table

To test the result, use the following in findMulti() option:

array(
  'pager-dir' => 'rev',
  'sort' => 'workflow_last_update_timestamp',
  'order' => 'desc',
  'limit' => 100
)

Change-Id: I2cb045d199e3364e4da38fd196a42e06ed721735
Merge "Add Sorting to topic list based on last updated timestamp"