Tidied up audit records.
Introduced checking for mid-air collisions.
Fixed minor defects and improved documentation.
Refactored fields so that derived fields and ordinary fields can be
processed together. Now derived fields appear in their correct
position as specified by the sort order.
New derived fields to determine whether a subdocument exists and to
retrieve a field value.
Fixed bug - hard coded module name.
Added audit trails to documents (and web output).
Logical fields are now correctly formatted in view mode.
Text fields are correctly escaped in view mode.
Dynamic drop-downs (derived sets) are now working.