kiji-scoring: SCORE-177. Support attaching a Freshener to a map-type family

issue: https://jira.kiji.org/browse/SCORE-177
review: https://review.kiji.org/r/1830
commit: https://github.com/kijiproject/kiji-scoring/commit/0f37f19d6e89c0e4318a6d33200c167f9088d69f