Added optional scrollbar to be able to scroll back through waterfall.
When scrolling is enabled:
Can adjust power scale for complete waterfall, not just future spectra.
Waterfall time axis can use local time or UTC.
Waterfall not lost when resizing window.
Can now zoom when device is stopped.
Added Min averaging type.
Added button to load spectrum from .csv file.
Add button to save spectrum/waterfall to .png or jpg.
Changed show all controls button to a combobox with choices of Min/Std/All (Minimum/Standard/All).
Changed some buttons in spectrum GUI from QPushButton to QToolButton so their size matches the others.
Fix spectrum from displaying a mixture of old and new spectrums (m_currentSpectrum was a pointer to SpectrumVis buffer).
Added M1 and M2 memories to allow display of reference spectra.
Added math operations to allow spectrum to be difference of current spectrum and either memory or a moving average.
Fixed measurement counts, so they are performed once per spectrum, not on displayed spectra.
Added spectrum mask measurement, to check when a spectrum exceeds mask held in M1 or M2.
Optionally display power/frequency under cursor in status line.
Optionally display peak power/frequency in status line.
Fix incorrect nyquist sample replication, when zoom used.
Fix cursor not changing from resize to pointer when moving over spectrum measurements window.
Add spectrum colour setting.
Frees memory allocated
in SpectrumMeasurements::createPeakTable(int) .../sdrgui/gui/spectrummeasurements.cpp:303
in SpectrumMeasurements::createPeakTable(int) .../sdrgui/gui/spectrummeasurements.cpp:304
