Centralize Ticket management of persistent stores (#682)

* Centralize Ticket management of persistent stores

persistence package with Manager & Ticket will handle
all the details about keys, secrets, ticket into cookies,
etc. Persistent stores just need to pass Save, Load &
Clear function handles to the persistent manager now.

* Shift to persistence.Manager wrapping a persistence.Store

* Break up the Redis client builder logic

* Move error messages to Store from Manager

* Convert ticket to private for Manager use only

* Add persistence Manager & ticket tests

* Make a custom MockStore that handles time FastForwards