Allow Primary and Secondary Categorisation For Reporting

The ADREP 2000 report categorisation system used by ICAO requires that occurrence reports are categorised by a primary category as is currently possible with Air Maestro.
They also require that reports be categorised by one or more secondary categories to include other aspects of the occurrence.

I would like to see another report category tree which behaves like a checkbox list to meet this standard. This would also require the safety dashboard to be expanded with a secondary category widget.