kiji-express: EXP-400. Update TimeRange to be structured like SchemaSpec/PagingSpec.

issue: https://jira.kiji.org/browse/EXP-400
review: https://review.kiji.org/r/1560
commit: https://github.com/kijiproject/kiji-express/commit/e0688350f2047e545bcc232868fc0b25ffad01e0