Bug 13052 - OPAC Cart JavaScript is included twice in the footer

Bug 13052 - OPAC Cart JavaScript is included twice in the footer

The external JavaScript file which powers the OPAC Cart should not be
included twice. The correct instance is the one which comes after the
definition of MSG strings.

To test you must have the opacbookbag system preference turned on. In
Bootstrap OPAC, test adding some items to the Cart and confirm that Cart
operations work correctly.

Signed-off-by: Chris Cormack <chris@bigballofwax.co.nz>
Signed-off-by: Katrin Fischer <Katrin.Fischer.83@web.de>
Cart is still working as expected, passes tests and QA script.

Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>