Updated constraints galore!

Updated the constraints that were missing in previous builds for the
SearchViewController and SearchResultsTableViewController.

Moved the loadData() method out of the viewDidAppear function of the
MyConversationsTableViewController and MyItemsTableViewController just
as had done previously with the ListingsTableViewController.

Continued work on the new implementation of
ListingPFQueryTableViewController. May kill this/ the link when the
build is next released. Want to continue to keep the Storyboard as well
as the code (.swift file) for a possible Phase 1 implementation. If
employed, will want to port over to all current UITableViewController
views.