Changes

Summary

1. removed junk;
2. tuned proofs;
3. enforce full build, after significant changes in Isabelle/Scala;
4. clarified compiler options: show relevant warnings;
5. tuned --- avoid compiler warnings;
6. clarified signature --- fewer warnings;
7. clarified signature --- fewer warnings;
8. tuned --- fewer warnings;
9. more robust ordering (see also 88c96e836ed6);
10. proper scala.collection.immutable;
11. tuned --- fewer warnings;
12. tuned --- fewer warnings;
13. tuned;
14. tuned --- fewer warnings;
15. tuned --- fewer warnings;