Changes

Summary

1. tight representation of types / terms / proof terms (presently unused);
2. merged
3. reduce redundancy: avoid huge lists;
4. more detailed profiling including "names"; avoid overlapping results;
5. tuned;
6. misc tuning and clarification;
7. slightly more compact heap: better sharing of persistent tuples;
8. added method to generate build schedules directly;
9. clarified load vs. apply vs. make;
10. tuned;
11. tuned heuristic;
12. use cpu time for approximation;
13. lower bound for approximated times;
14. use full timing information in build schedule;
15. consistent hosts ordering;
16. filter hosts properly;