kiji-schema: SCHEMA-840. Iterable based (instead of iterator based) KijiResult API

issue: https://jira.kiji.org/browse/SCHEMA-840
review: https://review.kiji.org/r/1965
commit: https://github.com/kijiproject/kiji-schema/commit/2c26755dd68730e9fdc83baec60516ed26cd38ed