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

mappings/DwC2-VegBIEN.specimens.csv, VegCSV-VegBIEN.specimens.csv: taxonoccurrence: Map everything except occurrenceID (which is globally unique) to new authortaxoncode, which only needs to be unique within the locationevent

schemas/vegbien.sql: taxonoccurrence: Renamed taxonoccurrence_locationevent_1_to_1 to taxonoccurrence_unique_within_locationevent and added new authortaxoncode to it

schemas/vegbien.sql: taxonoccurrence: Added authortaxoncode to store unique keys that are unique within the locationevent rather than within the datasource

inputs/SALVIAS-CSV/maps/VegCSV.organisms.csv: Added _alt to height_m, stem_height_m to choose between them when both are specified (rather than having bin/map choose their priority order based on their order in the map). Note that when both of the heights are specified, they are always either the same, or height_m is invalid (see <https://projects.nceas.ucsb.edu/nceas/projects/bien/wiki/SALVIAS_issues#Some-organisms-have-one-stem-but-different-heights-in-the-organisms-and-stems-tables&gt;).

bin/map: collision_suffix: Setting back to _alt to test if _merge caused the SpeciesLink slowdown. SpeciesLink contains a huge number of equivalent columns due to each DwC term being present with namespaces for all versions of the DwC schema, and these columns can be combined either using _alt or _merge. _merge is only useful if the values in different versions of the same DwC field are different, which is not likely the case.