Changes

Summary

1. tuned;
2. special case for local contrib, e.g. lxbroy10;
3. merged
4. tuned signature;
5. tuned;
6. clarified task logging via log service;
7. more explicit management of tasks; separate logger thread with exclusive access to main.log;
8. tuned;
9. added clone_repository; tuned;
10. support remote repositories via ssh command execution; tuned;
11. tuned signature;
12. modernized;
13. separate type class for arbitrary quotient and remainder partitions
14. stripped dependency on pragmatic type class semiring_div
15. simplified: no internal state for Mercurial;
16. explicit indication of Admin tools;
17. clarified files;
18. explicit timezone for the sake of lxbroy10;