SCHEMA-1. Adds a unit-test for schema validation on write.

Also adds Kiji.getAdmin().

Signed-off-by: Aaron Kimball <aaron@wibidata.com>
SCHEMA-19. Unit-test that write/read a final column

Signed-off-by: Aaron Kimball <aaron@wibidata.com>
SCHEMA-20. Improve validation of cell schema changes.

Counters must specify schema storage 'final'.
Final columns require inline schema specifications and cannot change.
Schema storage cannot be modified.