Changes

Summary

1. merged
2. Simplified some proofs
3. clarified db content: avoid redundancy of historic ML_IDENTIFIER;
4. merged
5. proper filterNot, not filterNot-not;
6. option build_hostname allows to change hostname easily;
7. clarified permissions of build.db, following server.db;
8. enforce rebuild of Isabelle/ML, after various changes to build database management;
9. misc tuning and clarification: more uniform use of optional "sql" in SQL.Table.delete/select;
10. tuned: fewer warnings in IntelliJ IDEA;
11. clarified init_database vs. update_database: implicitly assume fresh "instance";
12. clarified Build_Process.Context: cover all static information;
13. tuned whitespace in generated SQL;
14. tuned: prefer typed operations;
15. clarified signature: more concise operations;
16. more robust options in "prefs" format: avoid odd control character;
17. proper settings for hostname: allow to adjust it in user space;
18. support for build database: still inactive; more detailed Build_Job.Node_Info;
19. tuned signature;
20. clarified signature: more robust operations;
21. tuned;
22. tuned;
23. more operations;
24. clarified signature: more operations;
25. clarified signature;
26. clarified signature: more robust (see also cf2ef4be3630);
27. unused (see also 7b318273a4aa and a1fb4d28e609);