Bug 36498: Add ability to set item group display order from additem.tt

Bug 36498: Add ability to set item group display order from additem.tt

To test:
1. Apply patch, restart_all
2. System preferences -> EnableItemGroups, set to 'Enable'.
3. Find a record and create at least 1 item group.
4. Go to Add item
5. Scroll to the bottom and look for 'Options' underneath 'Add to item group'
6. In the dropdown select 'Create new item group'
7. There should be fields for 'Name' and 'Display order'.
8. Make sure you can add a new item group with and without a display order set. If no display order is set it should default to 0.
9. Try to add a non numerical display order, you should not be able to.

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>
(cherry picked from commit 49c55a03e70d4f4c7362cf45a5103f58c694af01)
Signed-off-by: Lucas Gass <lucas@bywatersolutions.com>