kiji-rest: REST-54. Supports per request freshening parameters.

Freshening parameters are issued in the URL query using 'fresh.' prefix.

issue: https://jira.kiji.org/browse/REST-54
review: https://review.kiji.org/r/1242/
commit: https://github.com/kijiproject/kiji-rest/commit/cda7c568a4ce60b01fc6da84796cfebc5f2f22b2