It's only good for dispersive media; specifically, a text file with
three floats per line: 'wl n k'.
A custom script was used to convert Maxim's data.
It's very fast, and has a ton of options.
Only the most important are exposed in the node for now.
A bug in MPL plotting aspect ratio declaration on MPL axis object was
fixed by manually running `set_aspect('auto')` after the fact.
It shouldn't do anything, and it doesn't, other than fix the bug :)
Also brought the plotting function of the viewer to parity with
the 3D preview, so the "Auto Plot" button works as expected.