Move token persistence classes to token.persistence module

Create and move all token persistence code to a new token.persistence
module. This allows the token_provider_api to utilize the token
persistence service without introducing circular dependencies. A proxy
class, that will log a deprecation message if instantiated, has been
created for both the token.core.Manager object and token.core.Driver
object. These proxy objects are slated for removal in the K cycle.

Change-Id: Iae1240c6de4382332b967926efe31f5355554f6e
bp: non-persistent-tokens
add internal delete notification for endpoint

I think endpoint is not an important resource which other projects would
pay close attention to. So I think an internal notification is enough.

Change-Id: Ie42f2c867ea70fd41583151da0be19b9db682dad
Closes-Bug: #1337763
Merge "Move token persistence classes to token.persistence module"
Merge "add internal delete notification for endpoint"