Feature 2930: Eliminate hardcoded /bin/echo path in acceptance tests

To improve cross-platform compatibility, eliminates acceptance test path hardcoding of /bin/echo, as well as adjacent "mkdir" an "ln" commands in 10_files/02_maintain/staging/copy-select-link-dereference.cf, taking advantage of the mechanism in the "G" bundle which finds the correct local-platform paths for a list of common commands.