Changes

Summary

1. more robust: defer error in sessions structure to build process;
2. merged, with minor edits: Admin/PLATFORMS, CONTRIBUTORS;
3. Added tag Isabelle2021-RC3 for changeset 02422c9add5e
4. provide naproche-20210124 (inactive);
5. follow stackage update;
6. tuned name, e.g. relevant for Naproche-SAD debugging in Isabelle/jEdit;
7. more operations for client connection;
8. fewer warnings, notably in Naproche-SAD;
9. suppress bundled Naproche-SAD component: it is in conflict with building the same from sources;
10. more robust etc/settings;
11. IDE support for Naproche-SAD;
12. proper path;
13. support isabelle components -u and -x;
14. proper typescript version, required for "vsce package";
15. auto-update;
16. auto-update;
17. proper type constraint;
18. VSCode extension for official Isabelle release;
19. proper message;
20. unused;
21. proper heap_free;
22. suppress markup for literal tokens with block control symbols, for better PIDE/HTML output (see also d15fe10593ff);
23. clarified documentation concerning macOS Big Sur;
24. more systematic java-gui-setup, also for "isabelle jedit" command-line tool;
25. updated to flatlaf-1.0-rc1;
26. tuned;
27. tuned proofs;
28. tuned;
29. obsolete;
30. clarified platforms;
31. more NEWS;
32. workaround for Big Sur fullscreen mode: better support for JDialog windows (e.g. Find on top of main View);
33. clarified app identification, potentially relevant for macOS "defaults";
34. updated documentation: HIDPI works smoothly thanks to FlatLaf;
35. updated for release;
36. updated screenshot;
37. clarified reports before errors: support completion of bibtex entries in Isabelle/Scala (amending d01ea9e3bd2d);
38. tuned;
39. proper theory_long_name;
40. updated screenshots;
41. more robust GUI, notably for Big Sur full-screen where the hypersearch panel becomes a separate maximized window;
42. revert 1105c42722dc on isabelle-release branch;