kiji-model-repository: KIJIREPO-8. Implement an API for attaching a freshener to a column which freshens with model in model repo.

issue: https://jira.kiji.org/browse/KIJIREPO-8
review: https://review.kiji.org/r/1137
commit: https://github.com/kijiproject/kiji-model-repository/commit/f527871484f62d30421c04bcec908748fdf2978e