[CDAP-774] Made application lifecycle namespace-aware

Added ``AppLifecycleHttpHandler`` for managing v3 Application Lifecycle Management APIs
Think theres a (potential) bug here... If the response is sent here, you still execute the rest of the code in the method that calls this. 

Better would be to return a boolean from this method (maybe call it `isValidNamespace`), and then do the responding from whoever calls it. That way the flow becomes cleaner to read.