Bug 21646: Clean up Overdrive template

Bug 21646: Clean up Overdrive template

This patch modifies the OverDrive administration page to correct some
markup issues:

 - Switch to Bootstrap grid
 - Add missing header search box
 - Add missing DataTable configuration
 - Remove unnecessary fieldset

To test you do not need to have OverDrive credentials. Apply the patch
and go to System preferences -> Enhanced content -> OverDrive. In the
description of the "OverDriveAuthName" preference, follow the link to
manage "individual branch authnames."

 - Confirm that the page looks correct, including the header search
   box, page title, and breadcrumbs
 - Confirm that the page adjusts well to various browser window sizes.
 - Confirm that the DataTable works correctly.

Signed-off-by: Liz Rea <wizzyrea@gmail.com>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>