Overhaul plot-system

[thomasnordquist]

Add plotting feature for JSON values: #77)

The current plotting library might have to go.

Issues

• No auto-scaling / auto-truncating for axis descriptions: Y-axis labels truncated with larger numeric values #84
• The bezier-curves seem to be sometimes faulty, plot showing multiple y (f(x)) for a single x.
• There also might be a update-issue, values on the x-axis seem to be clustered, even though all points should be equidistant on the x-axis.

~100 random values, 1 second apart, default resolution, mac. (reproducible)

[thomasnordquist]

Fixed a lot in #8266a87417dbea4b199744e49c93a58f3f962ca5