Add subscription configuration to doap.n3
add subscription class

this class implments Zend_Feed_Pubsubhubbub_Model_ModelAbstract and Zend_Feed_Pubsubhubbub_Model_SubscriptionInterface

data stored only in session for the moment
add PubSubHubbub_ModelHelper class

its purpose is to add a scription model if it's does not exist on the runtime
implement PubsubController (add subscription action)
rewrite PubsubControllerTest and TestHelper

test for subscription action