Implement variable load scan on the mass tester active board

• Efficiency scan for mass tester.

• setLVPS renamed to setVin

• getVset renamed to getIload

• pbv3_active_calibrate.cpp outputs variable load calibration to argument

• External variable load current added to PBv3TBSingle.cpp

• initLVPS removed from PBv3TBSingle/Massive, moved to base class PBv3TB.cpp

• pbv3_fancy_load allows for reading of current from external load as opposed to active board load.

• pbv3_active_debug toggles multiplexer readings on the AMAC and reads from the active board ADC using getVout().

• pbv3_whatisalive added. toggles OF