Bug 24860: Add reserves.item_group_it

Bug 24860: Add reserves.item_group_it

This feature builds upon bug 24857 and allows placing holds that target a specific item group of a record. It is patterned after the feature that allows limiting hold selection by itemtype ( AllowHoldItemTypeSelection ).

Test Plan:
1) Apply bug 24857 and this bug's patches
2) Run updatedatabase.pl
3) Restart all the things!
4) Enable the sysprefs EnableVolumes and EnableVolumeHolds
5) Create a record, items and item groups, with each item being assigned to
an item group
6) Place a hold for a patron
7) Note the new selector to choose an item group in addition to record and item level holds
8) Place an item group level hold
9) Check in an item from the record that is not part of that item group
10) Note the hold is not trapped for that item
11) Check in an item from the record that *is* part of that item group
12) Note the hold is trapped for that item
13) Place an item group level hold for another item
14) Run the holds queue builder
15) Note the holds queue targets only items from that item group
16) Check out all the items of that item group to other patrosn
17) Re-run the holds queue builder
18) Note the holds queue no longer has a line for that hold,
    as all items that could fill that hold are now unavailable

Signed-off-by: Andrew Fuerste-Henry <andrew@bywatersolutions.com>
Signed-off-by: Rebecca Coert <rcoert@arlingtonva.us>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>