fix(game): make current partner and pet null if pinit does not contain them

Merge pull request #47 from Rutherther/feat/pass-nullable

Pass CanBeNull to string serializer and converter

feat(packets): update packets to not use nullable if not needed

Merge pull request #45 from Rutherther/feat/mates

Add support for mates

fix(packets): correctly represent finfo

fix(packets): make nullable wrapper a class

feat(game): add mates processing

feat(game): add friends processing

feat(game): add group processing