mappings/VegCore-VegBIEN.csv: location.authorlocationcode mappings: Placed inside "if subplot" _if statement along with sourceaccessioncode to reduce the number of separate _if statements needing a condition mapping

xml_dom.py: NodeEntryIter: Support entries with multiple children

xml_dom.py: replace(): Support a list of new nodes to replace the old node with

xml_dom.py: Moved only_child() near related method has_one_child()

xml_dom.py: only_child(): Raise exception instead of failing assertion. Include invalid node in exception message for easier debugging.

xml_dom.py: Added only_child() and use it where its definition was used

mappings/VegCore-VegBIEN.csv: Changed _merge to _join wherever the duplicate-eliminating functionality of _merge is not needed and a simple concatenation of non-NULL values is sufficient

xml_func.py: Added _join() simplifying function

schemas/functions.sql: Added _join()

mappings/VegCore-VegBIEN.csv: Moved "if subplot" _if statement around /location/parent_id and /location/sourceaccessioncode themselves, so that only one _if cond mapping for subplot is needed. Note that this is only possible because this _if statement uses _exists, allowing it to be fully evaluated by the XML template simplifying mechanism, which supports subtrees as arguments to _if.