Bug 20876: The form_serialized_itype cookie is not used and should be removed

Bug 20876: The form_serialized_itype cookie is not used and should be removed

This patch removes references to a form_serialized_itype cookie which
appears in the code as part of the process of storing information used
in the generation of the "Return to the last advanced search" link.

To test, apply the patch and perform an advanced search in the OPAC
using several search options including a limit by item type. From the
search results page, follow the "Return to the last advanced search"
link. The advanced search form should appear with all the search options
you submitted before.

Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>