kiji-rest: REST-70. Entity ids with components must be specified as true JSON arrays.

issue: https://jira.kiji.org/browse/REST-70
review: https://review.kiji.org/r/1353
commit: https://github.com/kijiproject/kiji-rest/commit/19917d4f1683479b1384392a6d90678e4b8f66e5