Add collect learner's grouping

Groups are pre-defined, ie., 1st grade, 2nd grade. etc. Each group
has 1-to-1 relationship to an aproximate age. Therefore, when users
select groups they are actually storing an aproximate age, that can
converted later to a group.

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

Pair each spent-time with the proper launch-time. Send
this information as a list of these pairs.

This version includes enhancements by Martin Abente Lahaye.

Signed-off-by: Martin Abente Lahaye <tch@sugarlabs.org>
Make group logic optional

Fallback to empty string if Group bits are not there.

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