Architecture notes

There are two sources of configuration information:

(0) CORE: (version 0.1) inferred from project stored as:  PROJECT/.containenv/Dockerfile
(1) SUGGESTED_PREFERENCES:   (version 0.2) in PROJECT/.containenv/SUGGESTED (overridden by PREFERENCES)
(2) PREFERENCES: (version 0.1) ${HOME_ENV}/containenv/preferences.ini

