Changes

Summary

1. alternate AFP tests on lrzcloud2, to fit better into one day;
2. merged
3. support document preparation from already loaded theories;
4. clarified GUI events;
5. clarified GUIs: keep related buttons together;
6. proper program name, e.g. for session "Intro";
7. clarified GUI events: reset everything on session context switch;
8. clarified GUI events: ensure fresh output when switching pages;
9. clarified GUI: avoid odd jumping pages on "Cancel";
10. clarified GUI events;
11. more accurate output: avoid output_body from last run;
12. more accurate output: avoid output_main from last run;
13. removed unused operation from 3f50b24909df;
14. clarified guard: avoid spurious auto builds;
15. automatically build document when selected theories are finished;
16. more accurate Word.capitalize: do not touch name;
17. defer build until document nodes are ready;
18. clarified signature: prefer semantic status;
19. removed obsolete parameter (see 7c23db6b857b);
20. clarified Document_Editor.Session: more explicit types, more robust operations; eliminated await_stable_snapshot in favour of delay_build;
21. more operations;
22. clarified operation (without change of signature!);
23. pointless
24. Lots more new material thanks to Manuel Eberl