Changes

Summary

1. enforce rebuild of Isabelle/ML, after various changes to build database management;
2. more detailed table "isabelle_build_serial": allow to monitor activity of build_process instances;
3. tuned output;
4. clarified database content: store actual value instead of index;
5. more robust: disallow override;
6. tuned messages;
7. more complete coverage of non-final Progress methods, notably for Server.Connection_Progress;
8. clarified signature: manage "verbose" flag via "progress";
9. removed unused arguments: avoid ambiguity concerning progress/verbose;
10. clarified protocol for "verbose" messages;
11. clarified signature: manage "verbose" flag via "progress";
12. tuned;
13. tuned;
14. more operations;
15. tuned signature;
16. more robust: proper bound checks;
17. enforce rebuild of Isabelle/ML, after various changes to build database management;
18. clarified modules;
19. clarified signature: manage "verbose" flag via "progress";
20. clarified treatment of "verbose" messages, e.g. Progress.theory(); always store messages within database, with explicit "verbose" flag: client-side will decide about output;
21. proper "val verbose" (amending 2e2b2bd6b2d2);
22. tuned whitespace;
23. more robust signature: avoid totally adhoc overriding (see also Build_Process.progress vs. build_progress);
24. support progress backed by database; moved Build_Progress.Context.progress/log to class Build_Process: database is available here;
25. tuned;
26. tuned messages;
27. clarified signature: require just one "override def echo(message: Progress.Message): Unit";
28. tuned signature;
29. tuned signature;
30. clarified signature: more uniform Progress.verbose, avoid adhoc "override def theory()";
31. proper Output.writeln_text (with clean_yxml) for all instances of Progress.echo;