Add option for custom x axis graphs

[aswerdlow935]

An option that would allow for the plotting of x and y coordinates [for example to show robot position or plot a value using a stored time, etc.] would be super useful. Maybe it could be done using the putNumberArray method so no wpilib changes would be needed.

[DigitalZilla]

I would like to second this. We were trying to plot our vision target crosshairs on an XY graph, but are unable to do so. Ideally, we'd like to be able to plot an arbitrary number of XY pairs on the same graph.