enforce consistent API behavior upon a missing UUID during a call to
hasUUID
add missing setModule(...) calls - these missing sets were leading to
assertion failure exceptions during change set writing.
improve API by adding null check to prevent null pointer
just documentation
fix informAboutUUID to be null safe - so toString() calls that are
attempting to report on a different failure don't themselves, fail.

Make writeExternal do hard checking for missing attributes - remove
silent defaults that would silently create change set files that
differed from the content of the database when assertions were disabled.