adding new octave

[nulinspiratie]

See the markdown file for a demonstration

Remaining To do items

• Add base class BaseFrequencyConverter
• Add IF_outputs to OctaveDownConverter
• Write Octave.initialize_default_connectivity
• Add Octave-related config entries to channels
• Add tests
  • Test Octave loading
• Consider including singleton QMM instance
• Add Literal type to QuAM type checking
• Avoid breaking change for FrequencyConverter
• Add documentation

Implementation choices

• I avoid using the default connectivity "connectivity": "con1". Instead, I always define all connections.
  The reason is more flexibility, plus the OPX connectivity is defined in the channel, not the frequency converters
• I ignored config RF_inputs/id/RF_source as "RF_in" seems to be the only option.
• When an RF_output only uses a single OPX output, I attach it to I_connection
• When LO_frequency is not specified, I don't add the frequency converter to the config

Future updates

• Potentially incorporate QMM, QM, QmOctave into Octave

[yomach]

Looks good, let's discuss the changes in 2.4.0