kiji-scoring: SCORE-170. Move static inner classes out of InternalFreshKijiTableReader

issue: https://jira.kiji.org/browse/SCORE-170
review: https://review.kiji.org/r/1736
commit: https://github.com/kijiproject/kiji-scoring/commit/dec8f0e9ed8af5dbb03373ccb72de1bc63993d50