Bug 16047 [Follow-up] Software error on deleting a group with no category code

Bug 16047 [Follow-up] Software error on deleting a group with no category code

This follow-up take the original patch a little further, making category
name required on the entry form as well. Without a category name there
is no label in the interface when selecting a category. That doens't
make any sense.

Also changed on the group entry form:

- Added "required" attribute to labels on required fields.
- Changed "Update" submit button label to "Submit."
- Added a "Cancel" link.
- Added the "validated" class to the form so that our built-in
  validation script will process it (not strictly necessary but makes
  the validation appearance more consistent).

Followed test plan, form displays and behaves as expected.
Signed-off-by: Marc Véron <veron@veron.ch>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Brendan Gallagher brendan@bywatersolutions.com
(cherry picked from commit df127ebad814ad1710b161b85a69d408de95de85)
Signed-off-by: Julian Maurice <julian.maurice@biblibre.com>