more accurate management of dependencies: change of build_uuid causes output of HTML, but already existing/current HTML is not produced again;

tuned signature: more general operations;

tuned: avoid premature File.read;

tuned signature: build_log db is specific to PostgreSQL;

maintain "uuid" column in session build database, to identity the original build process uniquely; implicit upgrade of PostgreSQL database, while SQLite is initially removed and created afresh;

tuned signature;