Changes

Summary

1. clarified signature: proper scopes and types;
2. maintain global state of document editor views, notably for is_active operation;
3. tuned signature;
4. tuned whitespace;
5. clarified modules;
6. clarified signature: more robust;
7. tuned;
8. clarified modules;
9. more specific GUI for document nodes;
10. tuned;
11. tuned;
12. tuned;
13. tuned;
14. tuned;
15. tuned;