Connect message does not work for Instrument with no get_idn command defined

When using instruments that do not have an "IDN" method the Instrument.connect_message does not work.

I propose resolving this by adding the following method to the Instrument base class.

    def get_idn(self):
        return {'driver': str(self.__class__), 'name': self.name}

I think it is quite useful to have this method be part of the base class as we also want to see this message for e.g., Dummy instruments or things like meta instruments.

Start by locating the Instrument base class and the Instrument.connect_message implementation. Check how connect_message handles instruments without get_idn, then verify the fallback for Dummy instruments and meta instruments produces the proposed driver and name information.