kiji-schema: SCHEMA-877. Implement KijiRowScanner on top of KijiResultScanner.

Utilize KijiResultRowData to implement KijiRowScanner on top of KijiResultScanner.

issue: https://jira.kiji.org/browse/SCHEMA-877
review: https://review.kiji.org/r/2058
commit: https://github.com/kijiproject/kiji-schema/commit/49421014413cbb999f501f800c236e53092c0bae