Fix for Bug 4950 - checkbox should be removed when can't place a hold

Fix for Bug 4950 - checkbox should be removed when can't place a hold

- Hiding form controls for titles which can't be placed on hold
- Highlighting hold blocked message for better visibility
- Showing table of blocked holds even if none can be placed on
  hold: hiding the table hides the messages explaining why
  titles can't be placed on hold
- Removing an unused line from the script which was leaving errors
  in the error log
- Consolidating error messages into one box which were displaying
  in two.
- Correcting link to unused opac-userdetails.pl

Signed-off-by: Nicole Engard <nengard@bywatersolutions.com>
Signed-off-by: Chris Cormack <chrisc@catalyst.net.nz>