feat: Provide way to override cookie name
Rationale
Cookies are permanent, and when we run lots of experiments that blow up cookies size. As cookies are signed - each one takes around 256 bytes. So, in our case we want to have a way to clear out old cookies. I will provide a couple of more proposals later to configure other cookie behaviour (e.g., we don't want cookies to be permanent - we're running short-living experiments, so 1 month is more than enough for us).
Related to #74
Edited by Doug Stull