Rxlab-instruments

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- Agilent:
- add ability to quenry frequency and power
- add power_on and power_off methods
- add deprecation warning to rf_power
- Generic:
- add sub-module for a generic lab instrument.
- Hittite:
- add ability to fine tune frequency, set timeout for socket
- Keithley:
- add Keithley 2602 SourceMeter
- Micro Lambda:
- add yig synthesizer
- add ability to read ID number
- Rohde & Schwarz:
- add support for spectrum analyzer

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- Change package name: SCPI-Lab-Instruments -> RxLab-Instruments
- Add modules for controlling Micro Lambda YIG tuned filters, Agilent 34410A/11A/L4411A multimeters, Agilent E8257D signal generators and Siglent SDS 1104X-E oscilloscopes.
- Update documentation.