kiji-express: EXP-441. Add convenience method for creating KijiInput from a table URI.

issue: https://jira.kiji.org/browse/EXP-441
review: https://review.kiji.org/r/1895
commit: https://github.com/kijiproject/kiji-express/commit/25d1a3d1e3285bdc34b9fe0460f911f6aabc11d0