Analog modulation for NI RFSG driver

[mgunyho]

Add functionality to enable analog (amplitude / frequency / phase) modulation for NI-RFSG based devices. Includes example code in the example notebook. Tested amplitude modulation with a PXIe-5654.

[codecov-commenter]

Codecov Report

Merging #130 (60758d6) into master (2fd9c39) will decrease coverage by 0.66%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master     #130      +/-   ##
==========================================
- Coverage   19.91%   19.25%   -0.67%     
==========================================
  Files         121      123       +2     
  Lines       14708    14627      -81     
==========================================
- Hits         2929     2816     -113     
- Misses      11779    11811      +32     

Impacted Files	Coverage Δ
...ontrib_drivers/drivers/NationalInstruments/RFSG.py	0.00% <0.00%> (ø)
qcodes_contrib_drivers/__init__.py	100.00% <0.00%> (ø)
...es_contrib_drivers/drivers/CopperMountain/M5180.py	0.00% <0.00%> (ø)
...contrib_drivers/drivers/NationalInstruments/DAQ.py	0.00% <0.00%> (ø)
...contrib_drivers/drivers/Tektronix/Keithley_6500.py	0.00% <0.00%> (ø)
...ontrib_drivers/tests/QDevil/test_sim_qdac2_init.py	100.00% <0.00%> (ø)
...rib_drivers/tests/QDevil/test_sim_qdac2_current.py	100.00% <0.00%> (ø)
..._contrib_drivers/drivers/GeneralMicrowave/GM349.py	0.00% <0.00%> (ø)
...codes_contrib_drivers/drivers/Holzworth/HS9008B.py	0.00% <0.00%> (ø)
qcodes_contrib_drivers/drivers/QDevil/QDAC2.py	96.35% <0.00%> (+0.02%)	⬆️
... and 1 more

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[astafan8]

thank you!