inputs/GBIF/raw_occurrence_record/run: added herbaria_filter.plant_fraction.csv_/make(), which exports the plant_fraction herbaria whose plant_fraction >= 0.8

inputs/GBIF/raw_occurrence_record/run: added plant_fraction.table/make(), which contains the plant fraction for each herbarium

lib/sh/db.sh: added mk_drop()

lib/sh/util.sh: to_file(): log $stdout so users can tell which file is being created by the command. for some reason, can't use `local redirs=(">$stdout")` because the redirections don't seem to be applied. can't yet use `log+ -2 echo_vars stdout` because log+ does not yet support negative adjustments (they cause PS4 to be emptied out before being re-prepended to).

bugfix: lib/sh/util.sh: log+(): adjustment < 0: need to enclose -$1 in $(()) so it gets evaluated before being used as an array index

lib/sh/local.sh: psql(): documented that --output is actually for query results, not echoed statements (and thus must be redirected back to fd 1 while fd 1 with the statements gets sent to the logging port)

lib/sh/local.sh: psql(): documented why can't use fd 11

lib/sh/local.sh: use @redirs instead of manual redirection to set up --output fd, so that the redirection will be echoed along with the command. for some reason, this requires switching to fd 13 instead of 11, because fd 11 gives a "/dev/fd/11: Bad file descriptor" error when 11 is set with exec right before the command instead of on the subshell the command is executed in. (13 was chosen rather than 12 because 2 is for errors, while *3 (or 3) is for logging.)

bugfix: lib/sh/db.sh: pg_export_table_to_dir_no_header(): inlined $(pg_header) so setting $cols wouldn't affect pg_export_table_no_header(), which uses it as a kw param

bugfix: lib/sh/util.sh: to_file(): require_not_exists check: missing `test` in `if "$if_not_exists"`