'disableNotificationsForNetworkActivity' to disable posting network activity notifications

With this, you're able to have operations not post notifications on start, finish and pause. 

I'm using this code in an application that has an AFHTTPRequestOperationManager do status checks of a server every second and I don't want the AFNetworkActivityIndicatorManager to respond to those requests. But I don't want it to be disabled application-wide, for I do want to display the Network Activity Indicator for other requests.