[CDAP-774] Made application lifecycle namespace-aware

Added ``AppLifecycleHttpHandler`` for managing v3 Application Lifecycle Management APIs
Hmmm, I think the ``AuthenticatedHttpHandler#getAuthenticatedAccountId`` was throwing a ``SecurityException`` (although I don't think that code could generate a SecurityException the way it is currently, it was just part of the method signature). However, that method has been removed now. I could remove this, but I think eventually we will have to throw a SecurityException if a userid is not allowed to perform an operation in a namespaceId. I agree that is future work though. Should we document/add a TODO here for now?