bug 9397 - Error Messages hard to find for Visually Impaired Users (Accessibility...

bug 9397 - Error Messages hard to find for Visually Impaired Users (Accessibility) [Returning Items] {REVISION 1.1}

testing procedure:
1. Check in Invalid Item
2. See that new header has been added. "Can't Check in"

Signed-off-by: Liz Rea <liz@catalyst.net.nz>
A followup may come that makes this text invisible, but this helps accessibility a great dea, and passes validation.

Signed-off-by: Jonathan Druart <jonathan.druart@biblibre.com>
Amended patch: replace "Can't Check in" with "Cannot check in" and
delete a h3 element with the same text in order to avoid duplicated
messages.

Signed-off-by: Chris Cormack <chrisc@catalyst.net.nz>