schemas/vegbien.sql: stemobservation: Renamed stemobservation_unique_accessioncode to stemobservation_unique_within_plantobservation and also apply it to NULL sourceaccessioncodes, so that a plantobservation can have a single stemobservation for its single stem's traits without needing a separate sourceaccessioncode for it

schemas/vegbien.sql: aggregateoccurrence: Removed redundant aggregateoccurrence_unique_accessioncode unique constraint, which has been replaced by aggregateoccurrence_unique_within_taxonoccurrence

schemas/vegbien.sql: plantnamescope: Added CHECK constraint to ensure that at least one key column is specified (an empty plantnamescope doesn't make sense; use NULL instead)

schemas/vegbien.ERD.mwb: Synced with schema

ch_root: Don't require both the input and output mappings to contain their respective new roots, since sometimes only one or the other root is being subset. This will occur, for example, in mappings that are flat on the input but normalized on the output, such as VegCSV.

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.

input.Makefile: Testing: diffing test outputs: Ignore changes in whitespace, due to e.g. different indent levels. This facilitates accepting tests when an element has been nested inside another element (or unnested), by showing only the opening and closing tags of the new outer element.

dicts.py: DictProxy: Fixed bug where default value for inner param needed to be created in the constructor, or else every default instance would use and modify the same dictionary

db_xml.py: put(): wrap_e(): Call augment_error() to add the current node to the error message

db_xml.py: put(): Raise an error if there are multiple fields with the same name, instead of silently overwriting the first with the second. This generally indicates the need to use `:[@merge=1]` on the fields in question.