Changes

Summary

1. clarified signature; sleep unconditionally: avoid aggressive database access;
2. clarified module signature and state;
3. tuned messages;
4. omit somewhat pointless message, following b7187d4cdf68;
5. more robust handling of uninitialized value, notably Build_Process.progress;
6. tuned
7. partially revert f1f08ca40d96: benchmark data needs to be present before timing data is loaded;
8. clarified module signature and state;
9. tuned signature: more protected operations;
10. database performance tuning: just one synchronized_database for main loop body;
11. tuned;
12. more robust: assume that database is exclusive for this Progress instance --- always close on exit (see also bf377e10ff3b);