Scope save/load traces from/to memory
While in memory mode added ability to save the 50 traces stored in the memory bank to file. It is also possible in the same mode to load traces from file to memory. See https://github.com/f4exb/sdrangel/tree/master/plugins/channelrx/chanalyzer#e-scope-trace-control-line for details.
Fixed separation between live and memory mode in particular the sample rate settings.
Spectrum changes
Reworked the histogram (phosphor) display:
- Removed references to "holdoff" replaced by decay divisor which it actually is. Works only when decay is unit so that the decay rate is one over the decay divisor value.
- A zero decay effectively keep histogram values forever. This is useful to keep the max hold (red line) until the clear histogram button is pressed.
- Reviewed the decay, decay divisor and stroke limits.
- Updated the color palette so that lower histogram values are rendered better. This will make the phosphor display more useful.
Other changes
- Spectrum: fixed the possible out of memory condition for large values of averaging size by capping the moving average structure to 1000 elements.