kiji-express: EXP-324. EntityId.fromJavaEntityId should be accessible on a framework level.

issue: https://jira.kiji.org/browse/EXP-324
review: https://review.kiji.org/r/1414
commit: https://github.com/kijiproject/kiji-express/commit/aa7bb299d678e0b2c531746b2af4827c992c94d1