Changes

Summary

1. clarified modules;
2. clarified signature: more operations;
3. tuned names;
4. clarified signature;
5. tuned;
6. tuned whitespace;
7. clarified signature;
8. tuned;
9. tuned;
10. clarified signature: prefer Same.operation;
11. tuned;
12. more zproofs;
13. more operations;
14. clarified modules; minor performance tuning;
15. minor performance tuning, following 703201dbd413;
16. tuned;