Graph: Add Indication, if measurement is out of visible range

[TheSlowGrowth]

If a measurement is out of the on-screen range in the graph/report, the software currently displays a blank column in the graph. A small arrow should be displayed instead to show that there's data off the screen. The arrow could be placed on the top, facing upwards, for measurements that are too high to be displayed. Or on the bottom, facing downwards, for results which are too low.