VegBIEN: Reversed aggregateoccurrence<->plantobservation relationship to point from plantobservation->aggregateoccurrence, so plantobservation could be scoped by aggregateoccurrence in the same way as all other core tables are scoped by their parent tables. This reversed direction was an anomaly due to the need to have a trigger auto-set aggregateoccurrence.count to 1 when there was an associated plantobservation. This was most easily accomplished on the aggregateoccurrence table itself, but required the reversed relationship. The trigger has now been reimplemented on plantobservation, which externally updates aggregateoccurrence.count.