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/1792
commit: https://github.com/kijiproject/kiji-scoring/commit/92a2ac5b228127888d2fc35c9680a75cc1d262d3