add edx's python load script

provides much better handling of course_id and events.  Originally
written by JM at edX, it was passed along to me as mostly-obsolete-
but-still-helpful code.  I only made slight modifications (print
periods, handle zipped files).  If this lives on in production then more
could be done with it
- better error handing, especially duplicates
- option handing
- incremental loads
remove broken "times per day" query
new loader lets us do coursedate m/r

To support this session now includes course in key.  Have to rereun
everything.

While in there also factor out total_time query into its own file since
that's just a simple aggregation.