Create a Moodle plugin that adjusts a student's grade

[afokou]

Depends on #21

[dnna]

It looks like we can use https://docs.moodle.org/30/en/Grade_import to import grades to Moodle.That means we can simply create another export format for grades in Pixelbonus and avoid creating a full-fledged Moodle plugin.

[dspinellis]

👍