Added basic peak autojump feature
Fixed max peak detection
This seems like a nice feature, however the repo of the developer hasn't been updated since Feb.  Seems like a clean merge.
Merge branch 'master' of https://github.com/divan/gqrx

Conflicts:
	applications/gqrx/mainwindow.cpp
	qtgui/plotter.cpp
	qtgui/plotter.h