Add page with cross-package how-tos

[kennedy-mindermann]

Add a page that contains cross-package how-tos.

@kdayday do you have a better idea of what should be included here?

[kdayday]

@kennedy-mindermann We probably need to brainstorm this, as well as desired/undesired redundancy with individual package how-to's. Some thoughts:

• A start-to-finish Sienna\Ops how-to, including building a system (PSY), running a PCM (PSI), analyzing results (PA), graphing results (PowerGraphics)
• Similarly, a start-to-finish Sienna\Dyn tutorial (PSY, PSID, PA, PowerGraphics, others)
• Probably also a Sienna\Data tutorial for symmetry, I'm less familiar with what that should contain outside PSY
• A Sienna\Ops to Sienna\Dyn cross-application tutorial, using operating points from PCM results to run dynamics simulations

Concerns to resolve, probably same as with SIIPExamples: How to include these tutorials in automated testing frameworks to catch breaking changes

[kdayday]

I split this out into #25, #26, #27, #28, #29 to match the 5 use cases we're highlighting on the main website, though we'll want to add more eventually