lib/sh/util.sh: command(): print <>file redirects before command, because they introduce it

lib/sh/util.sh: added starts_with()

lib/sh/util.sh: to_file(): use @redirs to echo and set >$stdout instead of setting it manually, which is possible now that the command() @redirs bug has been fixed

bugfix: lib/sh/util.sh: convention of fds to use for command-specific alternate stdin/stdout/stderr: changed to 40/41/42 because 10/11/12 are used by eval (which is used by set_fds()). use of fd 10/11/12 will cause hard-to-find silent bugs because exec will not print an error when these are used. documented why not to use other series of fds for this purpose:...

lib/sh/local.sh: psql(): use new psql() from db.sh instead of psql_script_vegbien/psql_verbose_vegbien. this requires setting local_pg_database=vegbien to replace vegbien_dest used by psql_*_vegbien.

lib/sh/db.sh: psql(): set $PG* connection env vars from our connection vars ($server, $user, etc.). use use_pg to import $database so it can be different from $database for MySQL

lib/sh/db.sh: added use_pg alias

bugfix: lib/sh/db.sh: psql(): added missing `--set ON_ERROR_STOP=1 --quiet` opts from psql_script_vegbien

lib/sh/db.sh: added psql(), which replaces psql_script_vegbien and psql_verbose_vegbien for general connections. it also supports separate command and stdin files, to allow using `\copy from pstdin`, with pstdin pointing to a separate, EOF-terminated CSV file instead of inlined with the command and terminated with the \. escape (which may be contained within the CSV file itself).

bugfix: lib/sh/local.sh: psql(): $file can't both be passed as a --file param and be prefixed with the necessary \set schema, etc. commands, so instead include $file when cat-ing stdin