Bug 1983: Checkout: Hold repquest when checking out an item already on loan or reserved

 Bug 1983: Checkout: Hold repquest when checking out an item already on loan or reserved

This patch allows to put a hold on an item that is already checked out or reserved.

To test:

- Check out an item A
- Put a hold on an item B
- Verify that the staff user has permission to put holds
- Check out item A to a patron X
- Try to checkout item A to a patron Y
- Verify that you see underneath the buttons for Checkin/Checkout a link
  with following text: "Click here to place hold for [Patron X' name]"
- Verify that the link is stylable (div class circ-scheckoutplacehold)
- Verify that the link takes you to the page to place a hold on this biblio
  for patron Y
- Do the same for item B and verify that it works for reserved items as well.
- Repeat steps above for a patron who has restrictions, verify that the link
  does not appear
- Log in with a staff member who has no permission to place holds
- Repeat steps above for a patron without restrictions, verify that the link
  does not appear.

Signed-off-by: Chris Cormack <chrisc@catalyst.net.nz>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Brendan A Gallagher <brendan@bywatersolutions.com>