Bug 35906: Remove preference and add override handling

Bug 35906: Remove preference and add override handling

This patch updates the bookable nature of items to allow setting at the
itemtype level and then overriding that setting at item level should you
so wish to do so.

We also now properly handle the item_level-itypes preference such that
we look at item or biblioitem level appropriately.

Signed-off-by: Esther <esther@bywatersolutions.com>
Signed-off-by: Paul Derscheid <paul.derscheid@lmscloud.de>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>