clarified signature;

more robust: make double-sure that heap digest is present;

tuned;

minor performance tuning: just one transaction for log_db without heap;

tuned;

proper store.cache.compress;

tuned whitespace;

clarified store_session: heap requires process_result.ok, but log_db is always stored; clarified ML_Heap.clean_entry vs. ML_Heap.init_entry;

unused;

tuned;