Improved spectrum analyzer mode

- Faster sweeps by changing 2.LO only when necessary and using 400kHz I2C frequency
- Added FPGA settings for selectable ADC samplerate
- Additional measurement with different ADC samplerate when signal ID is on to remove ADC images

Software/PC_Application/Traces/traceplot.h

@@ -19,7 +19,6 @@ public:
     virtual void setXAxis(double min, double max){Q_UNUSED(min);Q_UNUSED(max)};
 
     static std::set<TracePlot *> getPlots();
-    static void UpdateSpan(double fmin, double fmax);
 
 signals:
     void doubleClicked(QWidget *w);