Allow running the configuration utility script as a standalone script.

This makes it really handy for double-clicking on Windows if .py files are associated with the Python interpreter.
Extracted the aenea project root to make it easier to configure for other installation locations.
Don't copy over config.py so customizations in the Natlink copy won't be overwritten.
Merge pull request #13 from nirvdrum/simpler_config

Simplify configuration file and reloading code.