Issue #2259111 by katbailey: Add referrer URL as a context to target based on
CH-439: Create web storage buckets to more easily assign variations in expiration policy.
CH-439: Split cache expiration settings for decisions and visitor context and update admin tests.
CH-439: Set decisions to be cached per session as the default setting.
CH-439: Only one storage bucket for agent decisions.
Convert visitor context expiration to per-option setting.
Limit cache expiration settings to those options in the currently running campaigns.
Added original referrer url.
Add original referrer url and tests.