Renamed the `InstrumentBase._cfg` attribute to `_protocol`.
Updated `slave.cryomagnetics.mps4g` module to use `protocol` instead of `cfg`.
Updated `slave.signal_recovery.sr7225` module to use `protocol`
instead of `cfg`.
Updated `slave.lakeshore.ls340` to use `protocol` instead of `cfg`.
- Updated `slave.ls370` module to use `protocol` instead of `cfg`.
- Added missing relay commands, closes #150.
Updated `slave.srs.sr830` and `slave.srs.sr850` to use `protocol` instead of `cfg`.
Updated CHANGES
Merge branch 'feature-inject_protocol' into develop