Generate plots.xml file for view

[pshriwise]

It would be really useful to be able to generate a plots.xml file from the plotter so views can be reproduced with the openmc executable.

[yrrepy]

In the inverse, it would be useful to be able to use the plots.xml file in the plotter, to grab the material colors from plots.xml

But maybe this exists somehow? Like a mechanism that puts the info of plots.xml into a .pltvw?

[pshriwise]

Mmm that might be handy yeah. What I'd really like to do is add a color attribute to the Material and Cell classes. See openmc-dev/openmc#2506 so they can me made part of the model and separated from the plot specifications entirely