Matplot++ skeleton code

[Tyler-Lentz]

Reworking this PR to just include the skeleton code for this functionality since it changes how the polygon and polyline classes are handled, and so we can get the matplot dependency merged in.

Ideally this branch would have been called chore/matplotplusplus because that is more what this is, but there are some code changes so maybe it's a little bit of a feature as well.

Implementation will be in a separate branch

[Samir-Rashid]

What's the status on this? #51 is going to get merged in the next few days, so this should be unblocked after that.

[Tyler-Lentz]

Shoutout @AskewParity, the dubins unit tests caught their first error in the code base. I messed up resolving a merge conflict which arose from introducing the color data member to the XYZ coord struct, so the psi value was not being correctly set. Roughly 80% of the dubins tests started failing, so I found it right away.

[atar13]

Looks great. Structure of all the classes make sense. I like the use of std::optional. CMake is clean and works in the container.

Maybe we can add matplot to the playground integration test just so we can always verify that we can still include it.