Changes

Summary

1. option to bypass ttfautohint for experimentation (it can have adverse effects);
2. clarified settings: allow for more Java versions;
3. proper default;
4. clarified;
5. auxiliary operation for common uses of 'compile_generated_files';
6. merged
7. Free_Abelian_Groups finally working; fixed some duplicates; cleaned up some proofs
8. merged
9. fixes for Free_Abelian_Groups
10. updated screenshot;
11. more NEWS;
12. tuned;
13. merged
14. tuned;
15. documentation for generated files;
16. tuned;
17. type Path.binding may be empty: check later via proper_binding; clarified 'export_prefix' default;
18. clarified export_files: Isabelle_System.copy_file_base preserves given directory sub-structure; tuned concrete syntax;
19. proper .exe path for export;
20. updated to sqlite-jdbc-3.27.2.1;
21. added command 'compile_generated_files'; tuned signature;
22. tuned signature: more operations;
23. tuned signature;
24. tuned signature;
25. clarified signature: more explicit operations for corresponding Isar commands;
26. proper URL;
27. fixed markup in Poly_Mapping; Free_Abelian_Groups (but not yet imported by Algebra!)
28. More group theory. Sum and product indexed by the non-neutral part of a set