added lib/runscripts/schema.pg.sql.run and use it in inputs/.TNRS/schema.sql.run

inputs/.TNRS/schema.sql: generate from the DB using `rm=1 inputs/.TNRS/schema.sql.run export_` instead of being a hand-edited file. this makes it much easier to edit the (now frequently-changing) TNRS schema directly in pgAdmin (which is graphical), rather than having to manually copy SQL changes from pgAdmin to the file.

inputs/.TNRS/schema.sql.run: export_(): added usage

added inputs/.TNRS/schema.sql.run, which syncs schema.sql with the DB

bugfix: lib/sh/db.sh: pg_dump(): don't default $struct flag to on, because both structure and data should be printed by default

lib/sh/db.sh: pg_dump(): added create_schema= flag to remove CREATE SCHEMA statements (useful if the schema already exists)

bugfix: lib/sh/util.sh: set_fds(): remove empty redirects resulting from using `redirs= cmd...` to clear the redirs and then using $redirs as an array

fix: lib/sh/util.sh: set_fds(): documented that it does not currently support redirecting an fd to itself (due to bash bugs that require the dest fd to be closed before it can be reopened)

bugfix: lib/sh/util.sh: stdout2fd(): don't add >&$fd redirect if the fd is 1, because redir does not currently support redirecting an fd to itself (due to bash bugs that require the dest fd to be closed before it can be reopened)

lib/sh/util.sh: filter_fd(): factored out >() subshell command into stdout2fd() for clarity