Bug 29002: Add bookable state to items

Bug 29002: Add bookable state to items

This patch adds a bookable boolean to enable/disable the ability to book
an item ahead of time

Test plan
1) Navigate to the 'Items' tab of a biblio
2) Note the new 'Bookable' option and select at least one item to allow
   bookings to take place
3) Note that without any items selected as 'bookable' one does not have
   the 'Place booking' option or the 'Bookings' tab on the biblio
   details page.
4) Note that when at least one item is bookable, the place booking modal
   now only displays items that are marked as bookable in the item
   selection
5) Sign off

Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Janet McGowan <janet.mcgowan@ptfs-europe.com>
Signed-off-by: Caroline Cyr La Rose <caroline.cyr-la-rose@inlibro.com>
Signed-off-by: Laurence Rault <laurence.rault@biblibre.com>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>