mappings/DwC2-VegBIEN.specimens.csv: Added VegCSV mappings, to enable use of one VegCSV-VegBIEN mapping for specimens and plots data

inputs/XAL/maps/DwC.specimens.csv: Remapped FieldNumber to recordNumber because this historical DwC term (http://rs.tdwg.org/dwc/terms/history/index.htm#fieldNumber-2009-04-24) has close to the same meaning as recordNumber, but not the same meaning as the current fieldNumber term

inputs/SpeciesLink/maps/DwC.specimens.csv: Remapped fieldNumber to recordNumber because term usage was inconsistent with DwC definition. Datasources often confuse this term, because it seems like the collection number, but is actually the author code for the event (VegBank's authorObsCode).

mappings/DwC2-VegBIEN.specimens.csv: catalogNumber: Added additional VegCSV mappings for mergability. taxonoccurrence.authortaxoncode: Added alternative mappings from VegCSV for mergability.

xml_func.py: simplify(): Apply pass-through optimizations for _if statements with no condition (which means false). This faciliates automated testing after an _if statement has been added, because the put template provided as part of the automated test will only change for those datasources that actually have a condition entry for the _if statement, which greatly reduces the number of tests that need to be accepted. (Note that the path before the _if will still be included as an empty path if there are no other mappings to that table, because the _if statement does not surround it.)

mappings/VegCSV-VegBIEN.specimens.csv: Added DwC mappings, to enable use of one VegCSV-VegBIEN mapping for specimens and plots data

schemas/vegbien.sql: Moved collectionnumber from specimenreplicate to plantobservation to replace authorplantcode, since these terms are used analogously in plots and specimens data. This code is really the DwC recordNumber (VegBIEN collectionnumber), which "serves as a link between field notes and an Occurrence record, such as a specimen [or plots data] collector's number" (http://rs.tdwg.org/dwc/terms/#recordNumber). Also, this prevents a specimenreplicate from incorrectly being created when plots data provides an authorplantcode.

mappings/DwC2-VegBIEN.specimens.csv: Mapped individualID for mergability with VegCSV

mappings/DwC2-VegBIEN.specimens.csv, VegCSV-VegBIEN.specimens.csv: Split occurrenceID into occurrenceID and individualID, where individualID refers to the plant in plots data and occurrenceID refers to the specimen in specimens data. This prevents plant sourceaccessioncodes from being mapped to the specimenreplicate, which was messing up stems mappings for the parent plantobservation. It also avoids mapping the specimenreplicate sourceaccessioncode to additional tables where it isn't needed. (Note that occurrenceID is needed for location to ensure that each specimen gets its own location to make locationdeterminations on. Everything else is directly or indirectly scoped by location when its own sourceaccessioncode isn't specified.)

mappings/DwC2-VegBIEN.specimens.csv, VegCSV-VegBIEN.specimens.csv: taxonoccurrence: Removed catalogNumber mapping because the catalogNumber applies only to the specimen, not to the occurrence, especially in plots data