UI should alert user if it gets passed malformed data

Frontend applications should notify the user if it gets passed malformed data. For example, in the Oozie UI's initializeWorkflowData initializeNodeData, it tries to parse the data field as JSON, which raises an exception if it's not a JSON string. When this happens, it prevents rendering the workflow graph, and just looks like it's stuck waiting for data from Oozie. Instead it would be much easier to debug what's going on if the UI popped up an alert or something saying that the frontend received malformed data from the backend. This would make this bug much easier to debug.