Add a UISearchDisplayController & a search bar

Not adding the search bar as a subview is intentional; it will be set as the table view's header once the view is loaded.
Fixes a crash in the story detail view

The 'LoadMore' view is a section footer, not a cell, so we don't need to add 1 to the number of rows.
First pass at search functionality

Currently only displays the first 20 stories (paging of additional results is needed).