Documentation needs expansion

[nickelpro]

The example plugin is a good stop gap, but we desperately need documentation for every default plugin and interface, as well as the SimpleClient, and how to build your own client.

These things move fast, so there's some weight to not getting overly invested in docs right now. Still, it is easier to update docs than it is to write them whole-cloth for a late stage project. Skeleton work now will pay off later.

Not going to assign this as an August issue, but sooner rather than later I'm going to need to spend a couple days writing comprehensive on-boarding docs.