Moodle tables.
ie user -> userid in many tables, plus in user_students
start -> starttime and end -> endtime
I've just done all this as carefully as I could ... I don't think
I missed anything but it's pretty intensive work and I'd be fooling myself
if I didn't think I'd missed a couple.
Note that this version should pretty much be able to bootstrap itself
using PostgreSQL now ... but this is untested
moodler