Bug 13806: Sanitize inputs where creating Reports subgroup

Bug 13806: Sanitize inputs where creating Reports subgroup

This patch adds validation of report group and subgroup inputs so that
the user can't enter data into only one half of the group code/name
pair.

To test, apply the patch and go to Reports -> Use saved.

  - Create or edit a report which doesn't have a group or subgroup
    assigned.

  - Under "Report group," select the "or create" radio button.

  - Click the "Update SQL" button to submit the form without entering a
    group code or name. The form should require taht you enter data into
    both fields.

  - Enter data into the report group code and name fields. Add data to
    either the code or data field under "Report subgroup." You should
    not be able to submit the form without populating both.

  - Start over editing a report which doesn't have a group or subgroup
    assigned.

    - Select an existing group under "Report group."

    - Under "Report subgroup," select the "or create" option.

      - You should not be able to submit the form without adding data in
        both the code and name fields for the report subgroup.

Signed-off-by: Séverine QUEUNE <severine.queune@bulac.fr>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>