Change validators to use the validator_context

Change InstanceKeys to take a namedtuple for context

util/config/validators/__init__.py

@@ -15,6 +15,6 @@ class BaseValidator(object):
 
   @classmethod
   @abstractmethod
-  def validate(cls, config, user, user_password, app):
+  def validate(cls, validator_context):
     """ Raises Exception if failure to validate. """
     pass