[Feature Request] Support SI RF units & conversions

[dBitech]

Add support for RF units, and conversion between them.

Such as:
Vpeak = Peak Voltage of an AC signal.
Vrms: [Vpeak/sqrt(2)] = Root Mean Square Voltage.
uV: [Vrms * 10^-6] = RMS voltage in microvolts.
uVemf: [((2*Vpeak)/sqrt(2))*10^-6] = Open Circuit voltage in microvolts .
uVpd: [(Vpeak/sqrt(2))*10^-6] = Microvolt with load, When the signal has a matched load, 1/2 the voltage is dropped across the load. it is the same as uV, unit just explicitly defines as loaded voltage.
dBuV: 20log(uV) = decibel of RMS microvolt.
dBuVemf: 20log(uVemf) = decibel of emf (open circuit) microvolt.
dBuVpd: 20log(uVpd) = decibel of loaded microvolt.
dBm: 10log(mW) = Power measurement, decibel of power in mW
dBuW: 10log(uW) = Power measurement, decibel of power in uW

....

[df7cb]

RF units would be cool, but dBs don't fit into the current way it works (linear vs logarithmic scale). I'll see if I can think of a way to make it work.