NO3M modifications to SDR-SHELL v4.25

Check CFG window/tabs for configuration of most added features

Changes, additions, etc.:

* Ability to capture / snapshot GUI automatically or on-demand, saved as PNG to configurable dirctory [main config: General]

* Add hardware gain config option (calls setGain and sets input gain) [main config: IQ]

* Major changes to spectrum and spectrogram:

  > properly centered spectrum
  > re-implemented zooming
    * no effect on font size, etc.
    * linear interpolation when zoomed in, decimate w/ max value when zoomed out
  > user configurable Spectrum above or below spectrogram
  > user configurable Spectrum height -> 'N' to decrease, 'M' to increase
  > Many spectrogram color palette options (ie. WSJTX, FLDigi, GMFSK, Rocky, etc.) [main config: Spectrum]
  > custom colors for spectrum (separate dot/line and fill colors)
  > Spectrum dots or lines (connect dots), fill w/ solid or gradient option [main config: Spectrum]
  > Spectrum peak markers, average line, toggle on/off aperature lines [main config: Spectrum]
  > Spectrum normal and peak modes [button on bottom panel = SPEC NORM / SPEC PEAK, etc.]
  > Waterfall time markers /w automatic period [main config: Spectrum]
  > Manual or automatic aperature settings for waterfall (ie. gain and contrast) [MAN/AUTO button bottom panel]  
  > Numerous spectrogram scrolling options [main config: Spectrum]:
    * Waterfall down / up
    * Linrad style normal and reverse
    * SDR-shell style normal or reverse
  > click "CA" label (footer) to quick toggle aperature lines on/off
  > user configurable FFT/sec (Spectrum/Spectrogram)
  > user configurable FFT/line (Spectrogram), mean avg of FFTs if > 1
  > IIR filter (EMA) in time domain w/ user configurable attack and decay
    * Spectrum and Spectrogram have separate settings
    * Setting both attack and decay to 1.0 turns off averaging
  > Gaussian averaging in frequency domain
    * Spectrum and Spectrogram have separate settings
    * User configurable number of bins to average (2n+1)
    * Setting Bins to 0 turns off averaging
  
* frequency scale under spectum

  > mouse scroolwheel + Cntrl key zooming (increments by factor of +/- 0.1).  Also works w/ "Zoom + -" label in footer
  > middle click resets to 1:1 zoom
  > left click (tune), hover (show freq), and scroolwheel (tune) same as spectrogram / spectrum
  > right click to toggle between absolute (ie. 7040...7050) and relative (-1000...-500) scales (relative like original SDR-shell)
  > purple band indicator inlay behind scale ticks (user option)
  > Digital/WSPR segment inlays (user option)

* panning from one edge to other of spectrum at any zoom level (except full zoom out)
  > left click and drag spectrum or freq scale
  > left click + cntrl centers panning on filter passband
  > middle click + cntrl resets panning (centers on dial freq)

* CW mode changes
  > Frequency LCD readout indicates supressed carrier +/- "BFO" offset
  > yellow dotted dial line indicates supressed carrier (ie. dial freq in other modes)
  > red dial line indicates supressed carrier +/- bfo offset (ie. signal frequency)
  > BFO offset shown in passband scale
  > change BFO with ',' to decrease or '.' to increase
    * filter will be shifted an equal amount (affects both CWL/CWU filters regardless of current mode)
  > switching between CWL and CWU will flip around signal frequency
  > ALT + scrollwheel adjusts the filter symmetrically (also works for AM/SAM/DSB/FM modes)
  > SHIFT + scrollwheel adjusts filter offset, analogous to PBT (passband tuning)
  > SHIFT + middle click resets filter to center of passband

* Filters
  > "lower edge" of filter lower limit limited to 0 in LSB/USB/CWL/CWU modes
  > "lower edge" of filter upper limit limited to BFO offset in CWL/CWU modes
  > "upper edge" of filter lower limit limit to BFO offset in CWL/CWU modes

* frequency at mouse location over spectrum/spectrogram/frequency-scale is rounded to nearest step size (selected LCD readout)

* spectrum/spectrogram/frequency-scale left click to change frequency is rounded to nearest step size (selected LCD digit)

* added AGC OFF back in, also sets output gain to compensate

* added preamp and attenuator buttons (both configurable gain - right click to set) [DSP: Gain]

* added noise blanker #2 (ie. SDROM) (right click NB2 to set parameters) [DSP: NB}

* added receive spot tone with user configurable parameters tone / amplitude [main config: General]

* tuning direction same for softrock vs. rockbound modes

* fixed memory read/write/display issues w/ rockbound mode

* UTC time displayed in passband scale

* added --spectrum-size=<size> command line or SDR_DEFSPEC env variable option:
   > valid settings are 4096 (default) or 8192 depending on DEFSPEC in sdr-core
   > no need to set if using default 4096
   > 8192 requires running modified sdr-core

* added --rigctl-port=<portnum> (or -g) command line option
   > set rigctl/hamlib port to avoid conflict with running multiple instances
   > default is 19009 (originally 19090)

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Compile:

cd ./src
qmake-qt4
make
make install

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Get Dttsp / SDR-core here:
https://github.com/glenoverby/dttsp.git

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SDR-shell v4.25 (original source)
https://github.com/glenoverby/sdr-shell-v4.git