schemas/vegbien.sql: specimenreplicate: Removed no longer needed individual-column lookup indexes because the constraint-covering lookup indexes now handle lookups. This also avoids index bloat.

schemas/vegbien.sql: specimenreplicate: Added covering lookup indexes on the unique constraints to enable fast merge joins in column-based import

schemas/vegbien.sql: specimenreplicate: Added CHECK constraint which ensures that there is at least one key to sufficiently uniquely identify the specimenreplicate

inputs/CTFS/maps/VegX.organisms.csv: Mapped VegX sourceAccessionCode = VegBIEN plantobservation,specimenreplicate.sourceaccessioncode so that specimenreplicate would have a required key

mappings/VegX-VegBIEN.stems.csv: Sort the plantobservation.sourceaccessioncode/specimenreplicate.sourceaccessioncode mapping with the other _ifs so the adjacent node merging works properly and it gets created before _ignore removes voucherType

mappings/VegX-VegBIEN.stems.csv: Also map plantobservation.sourceaccessioncode to specimenreplicate.sourceaccessioncode so specimenreplicate always has a key and will never be underconstrained

xml_func.py: process(): Fixed bug where an evaluated XML function might create a node of the same name as an existing node, but these nodes would not be merged even though they referred to the same object, by merging siblings of a newly-evaluated (replaced) node if they have the same name

xml_dom.py: Added merge() and merge_adjacent()

xml_dom.py: replace_with_text(): Return the new node

mappings/VegX-VegBIEN.stems.csv: Indirect voucher mappings: Removed no longer needed ":[*_id/taxonoccurrence]" because a specimenreplicate is a taxonoccurrence, so it doesn't need to have an empty taxonoccurrence