Bug 29686: Adapt Koha to use new fulfillment API for OverDrive

Bug 29686: Adapt Koha to use new fulfillment API for OverDrive

This patch modifies the checkout_download_url routine in
WebSerivce::ILS::OverDrive::Patron

We now directly hit the fulfillment endpoint with redirects disabled
and fetch the URL

The overdrive.js is modified to use a single 'Get item' button for all
checked out items and to refer to the fulfillment page

To test:
1 - Enable all OverDrive system preferences
2 - Search on opac and confirm OD results returned
3 - Checkout an item
4 - Confirm you have the new 'Get item' button on 'OverDrive account'
    tab on opac-user.pl
5 - Confirm the 'Get item' button works

NOTE:
Most items will also show the 'Get item' button in results, however,
magazines may not as each checkout has a unique 'reserve id' and the
'parent' id is not checked in our current code

Signed-off-by: Andrew Fuerste-Henry <andrew@bywatersolutions.com>
Signed-off-by: Owen Leonard <oleonard@myacpl.org>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>