LCOE plot palette

[kevybear]

Currently, the LCOE plot cycles through a color palette so that every Individual Analysis run it uses the next three colors. I didn't think it was a problem unless other people wanted to compare lcoe plots side-by-side in which case it might pose a problem.

Trivial to implement (just change the palette to 3 colors), just a design decision. Can change whenever.

File to manipulate: plot_lcoe_csm.py in the WISDEM CSM assembly.