Fail-proof against broken scorers and setups
AWS: Optimize DB query for submission information.

Avoid n queries per submission to fetch submission result, token, files, etc,
by preloading them in the same query. Load time for a page with 1000
submissions goes from 30 seconds to about 1 second. Similar results with ES and
SS when they go to check on ALL THE SUBMISSIONS.
AWS: Improve performance of rankings page.
ContestExporter/Importer: change the --light behavior

And benefit from SubmissionResults and UserTestResults.
Adapted Test.py to isolate & task versions
Cleaned up cmsMake and added a comment in Test.py
Start fixing cmsMake
AWS: Log some generic exceptions to aid debugging.
AsyncLibrary.py: Aid debugging by printing tracebacks over RPC.
SS: addition