Bug 37681: Fix XSS in staff interface item URLs on detail page

Bug 37681: Fix XSS in staff interface item URLs on detail page

This patch uses Javascript objects and safe sinks to prevent XSS
in the item URLs on the staff interface detail page.

It also makes sure those URLs don't get double-escaped. Yippee!

Test plan:
0. Apply the patch
1. Add/edit an item with the following URL:
http://prosentient.com.au?q=http%3A%2F%2Fprosentient.com.au
2. Add/edit a different item with the following URLs:
http://prosentient.com.au?q=http%3A%2F%2Fprosentient.com.au |
http://prosentient.com.au?q=http%3A%2F%2Fprosentient.com.au
3. Go to the staff interface detail page
4. Notice that the URLs are not double-encoded!
5. Try out a malicious payload (talk to QA/security about this)
6. Confirm that the malicious payload fails to execute the XSS
7. Celebrate!

Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>