Buddy starter, new BuddyObject::initWithId, logout fix

* Added Buddy Starter sample that is a completely basic example of getting the SDK bootstraped and using the auth fail callback

* Add public initWithId ctor on BuddyObject to allow wrapping an object around a raw ID (e.g. profile picture ID).

* Fix logout to clear user token.

Interesting. So much of my design had revolved around not allowing this :).

Either way, #youdaboss