kiji-model-repository: SCORE-129. Repackage ScoringServer into a submodule of KijiScoring

issue: https://jira.kiji.org/browse/SCORE-129
review: https://review.kiji.org/r/1292
commit: https://github.com/kijiproject/kiji-model-repository/commit/30bfefbaa108b4cc421982cfea8f1abf636fb8d8