inputs/.TNRS/schema.sql: download_settings comment: changed name of button to Download settings, which had gotten auto-replaced to download_settings

inputs/.TNRS/schema.sql: Download settings table: renamed to download_settings because although Download settings is the verbatim name of the button that this info comes from, it is not necessary to name the table a particular way in order to match up data to it correctly, so we can just use the standard naming convention (wiki.vegpath.org/u-name#format) and avoid the need to enclose the name in ""

inputs/.TNRS/schema.sql: added Download settings table, which stores data from http://tnrs.iplantcollaborative.org/TNRSapp.html > Submit List > results section > Download settings > settings.txt

inputs/.TNRS/Source/map.csv: mapped datasetURL

inputs/.geoscrub/Source/map.csv: mapped datasetURL

mappings/VegCore-VegBIEN.csv: mapped datasetURL

mappings/VegCore-VegBIEN.csv: mapped datasetURL

fix: mappings/VegCore-VegBIEN.csv: source__modified_date: remapped to pubdate instead of datelastmodified because this is actually metadata for the source itself, rather than for the VegBIEN record of the source

fix: inputs/.geoscrub/Source/map.csv: source__modified_date: use the mtime of the CSV file instead, since this is closer to the actual version of the biengeo code at the time it was run

inputs/.geoscrub/Source/map.csv: mapped source__modified_date. note that the test must be run with inputs/.geoscrub/Source/run instead of `make inputs/.geoscrub/Source/test` to add these metadata columns to the staging table.