Add more specific documentation for options and features

[marcomangano]

Type of issue

• Documentation update

Description

We do not currently provide any documentation or more specific description of pyXDSM features, leaving the user to try directly from example scripts. Although their use is pretty intuitive, we need to better document these example files, and check if they cover all the available features.
There might also be value in briefly discuss how and when to use specific symbolism.

[jrram]

I'm not that familiar with the inner workings of pyXDSM. Maybe ask @JustinSGray ?

[cfe316]

I would be very interested to see this. Some questions I have that were not obvious even after reading the paper & watching John Jasa's excellent youtube series:

• Are there any syntactical differences between "solvers" and "optimizers" here?
• Are "implicit functions" (IFUNC) implied to have their own solver attached?
• How would I use a "design of experiments" driver? Or metamodel? The latter I can only see in Fig 12. of the 2012 paper, for the Bliss-2000 architecture.
• Several figures in the paper show a thin black process flow line with has vertices where there's no "data" being passed, only an intersection between the thick gray lines.