Improve speed of csv users import
Strangely, the users import script takes a very long time (about one tenth of a second by user) to "simply" insert a user and register him to a course.
I'm attaching an example file (which requires the previous creation of a course with code 01EBRP12012).
After importing, looking at the list of users, I can see there about 13 users created per second. For 300 users, it takes about one minute though (there must be something very long somewhere in the process).