Provide string messages to all exceptions thrown by Smack
Description
While it is good to have different exception types (`StreamManagementNotEnabledException`, `SmackException` and its subclasses) to distinguish programmatically, the exceptions thrown by Smack should also feature a human-readable string message, so they can help debugging when only the text but not the full stack trace is shown.
While it is good to have different exception types (`StreamManagementNotEnabledException`, `SmackException` and its subclasses) to distinguish programmatically, the exceptions thrown by Smack should also feature a human-readable string message, so they can help debugging when only the text but not the full stack trace is shown.