kiji-scoring: SCORE-127. Move helpful static functions to a ScoringUtils class

issue: https://jira.kiji.org/browse/SCORE-127
review: https://review.kiji.org/r/1239
commit: https://github.com/kijiproject/kiji-scoring/commit/d2b24666ad3955ab0ab4fcfeaeb7495e11d4299b