lib/sh/local.sh: added public_schema_exists (), ported from lib/import.sh

*{.sh,run}: use new echo_stdout instead of echo_stdin where applicable, for clarity

lib/sh/util.sh: added echo_stdout (currently just an alias of echo_stdin, because they are usable for the same purpose)

/run: moved geoscrub_input export into separate geoscrub_input/make () target

lib/sh/db.sh: pg_export_table_to_dir_no_header (): use to_file so that the file is autoremoved in case of error

lib/sh/util.sh: let (): renamed to let! so that let can still be used to evaluate whether a numeric value is 0 (yes, an ! is allowed at the end of a command name)

lib/sh/util.sh: moved canon_rel_path () into separate paths section

bugfix: : use new func_override for runscript inheritance instead of invoking the overridden function as a (command-line) target of the parent runscript. this ensures that the overridden function is run in the *same process as the calling function, so that $top_dir keeps the same value and runscript-relative paths continue to work.

lib/sh/util.sh: added func_override (), for use in runscript inheritance

lib/sh/util.sh: copy_func (): check that $from exists and $to does not exist (i.e. don't clobber existing functions). you can always first `unset -f` the function to get around the no-clobber restriction.