Changes

Summary

1. merged
2. maintain loaded_files for each theory;
3. clarified: more uniform results;
4. slightly more parallelism;
5. prefer sequential file-system access, but parallel parse;
6. tuned;
7. clarified pure_files, based on uniform loaded_files;
8. tuned;
9. tuned signature -- more readable output as Scala value;
10. more operations;