SCHEMA-471. Add system-2.0 and enable layout-1.3 to Kiji layout versions

- Update the default system version from system-1.0 to system-2.0.
- Fix bug in the HBaseTableLayoutUpdater when the layout descriptor doesn't have a layout ID.
- Small test cleanups.

issue: https://jira.kiji.org/browse/SCHEMA-471
review: https://review.kiji.org/r/1032