kiji-express: EXP-249. Refactor the KijiExpress Model Lifecycle into a separate project.

issue: https://jira.kiji.org/browse/EXP-249
review: https://review.kiji.org/r/1266
commit: https://github.com/kijiproject/kiji-express/commit/86b651a6fa0665e7b5cbf9ee1b749b6734448ebc