Migrate and store learners groups

Create a new grouping columns, update primary and foreign
keys and update insertion queries.

Signed-off-by: Martin Abente Lahaye <tch@sugarlabs.org>
Pretty json for test data

Thanks to http://jsonprettyprint.com and Manuel Quiñones.

Signed-off-by: Martin Abente Lahaye <tch@sugarlabs.org>
Move spent_time to launches

Launch time timestamps are now paired with the time in
seconds for which the activity was used.

This version includes enhancements by Martin Abente Lahaye.

Signed-off-by: Martin Abente Lahaye <tch@sugarlabs.org>
Re-order migration files

Swap the order between 010 and 009, to save troubles
to Uruguay downstream package.

Signed-off-by: Martin Abente Lahaye <tch@sugarlabs.org>