The completer now works for cmd_word that is a path name.
Prepare utilities for the next version.

Add docstring and a --force option to rm.py
selfupdate.sh now tries to delete unwanted development only files.
Merge branch 'master' into dev
Merge branch 'dev' into runtime-opt
Runtime optimization mostly works.

Enclosing env vars made clear. Shell script file contents are executed
in one batch to make env persistent during the execution.