Fix use of magic numbers in GtkGraph.
For those tempted to do it again, read the haiku in draw() and don't do that shit.
back to 60 seconds graph
history can now extend what is shown
add basic right click menu
for some reason i had to derive from Gtk::Button to get a click signal,
    this is weird
Merge remote-tracking branch 'origin/wip/timed-graph' into wip/looks-familiar

Conflicts:
	src/gtk/GtkGraph.cpp
	src/gtk/GtkGraph.hpp