schemas/VegCore/VegCore.ERD.mwb: specimen: split collection into orig,current_collection because the collection that scoped the accession_number (the orig_collection) is sometimes different than the collection where the specimen is now held (the current_collection, or specimen_holder_institutions), e.g. when the specimen is donated

schemas/VegCore/VegCore.ERD.mwb: collection: added institution, name to identify and scope the collection

schemas/VegCore/VegCore.ERD.mwb: changed taxon_name fkeys to taxon_concept where appropriate, and renamed the referencing columns to *_taxon_concept to clearly indicate the referenced table. taxon_concept fkeys are appropriate whenever a taxon is defined or associated with an observed entity, in which case the assertion is not just to a taxon name but to a defined taxon concept (albeit sometimes an unofficial taxon concept scoped by the collector or identifier).

schemas/VegCore/VegCore.ERD.mwb: specimen: added code_in_individual column

schemas/VegCore/VegCore.ERD.mwb: specimen: added fkey to individual for the individual the specimen was taken from

schemas/VegCore/VegCore.ERD.mwb: individual/stem_observation: made individual/stem nullable because there is not always enough identifying information (stem tag, etc.) to actually associate an identifiable individual with an observation

schemas/VegCore/VegCore.ERD.mwb: moved code from individual to individual_observation because the code is something applied at observation time, rather than something that can be used to track individuals between observations

schemas/VegCore/VegCore.ERD.mwb: moved collection_event from taxon_occurrence to specimen because only specimens are actually collected, while other taxon_occurrences (e.g. individuals) must be uniquely identified by some means that are shared between re-observations (e.g. the stem tag)

schemas/VegCore/VegCore.ERD.mwb: moved collector, collector_number from taxon_occurrence to taxon_observation because these are actually attributes that are available or assigned at observation time, rather than being intrinsic to the taxon_occurrence (which can be either an individual or a specimen)

schemas/VegCore/VegCore.ERD.mwb: method: colored it forest green like stratum because these are both tables in the same category (method), and forest green is the color VegBank uses for methods. (the fact that VegBank gives stratum the method color indicates that we are on the right track when we are treating stratum as a type of method that's essentially a height class.)