Bug 19129 - Follow-up - Add changes to patron duplicate warning

Bug 19129 - Follow-up - Add changes to patron duplicate warning

Adds logic from the previous fix to the brief patron summary
shown when checking a possible patron duplicate.

Bonus: Also fixes missing patron category description there.

To Test:
- Add 2 patrons
- Add a patron with the same surname and firstname as an
  existing patron in order to trigger the duplicate message
- Click "View existing patron"
- Verify display is correct when existing patron is
  - an organisation
  - not an organisation
- Verify that the patron category description shows

Signed-off-by: Aleisha Amohia <aleishaamohia@hotmail.com>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>