Mark notes as learned during database sync with Anki

[odakaui]

Expressions of notes that are mastered should be marked as is_learned = 1.

There might be a problem with marking expressions as is_learned. Anki could potentially have multiple cards per note. It appears that you can search for a card and then get the note for that card. However, it is unclear how anki defines mastered. This is potentially an additional feature that should have its own issue.