Added inputs/.TNRS/tnrs/tnrs.make to run tnrs_db on VegBIEN

Added tnrs_db to scrub the taxonpaths in VegBIEN using TNRS

Regenerated vegbien.ERD exports

schemas/vegbien.sql: taxonpath: Made it datasource-general and uniquely identified only by its taxonomicnamewithauthor so that the taxonpaths imported by the TNRS datasource will be matched and used directly when the other datasources are imported

schemas/vegbien.sql: taxonpath: taxonpath_unique_within_datasource_by_name unique index: Just do duplicate elimination on the taxonomicnamewithauthor, since that is now a required field and is generated by concatenating all the other fields. Note that the inserted row counts change slightly because the concatenation makes some names equal that are split among the fields differently, such as when the genus is included in the species field.

db_xml.py: put(): Added _alt optimization that just returns the first arg if it's non-NULL

sql_gen.py: Added is_nullable()

schemas/vegbien.sql: taxonpath.taxonomicnamewithauthor: Made it NOT NULL, so that all taxonpaths would have a concatenated name to feed to TNRS

mappings/VegCore-VegBIEN.csv: taxonomic terms: Changed _first to _alt because some datasources have NULL values in scientificNameWithAuthorship or scientificName, so it can't just be used in place of the joined-together taxonomic ranks

db_xml.py: put(): Parse input columns and process values in separate loops, so that structural XML function optimization code can be inserted between them