* UDP Message source can handle multiple data types
* Add a waterfall sink block
* Fix dependency issues with VOLK
* Add mean and max hold mode to the waterfall sink
* Add mean and max hold mode to the waterfall sink
* Install satnogs_waterfall.gp gnuplot script at
<install_prefix>/share/satnogs/scripts
* Automatically retrieve x and y axis ranges at the satnogs_waterfall.gp