Next steps on opmonlib documentation

[jcfreeman2]

It looks like there's a decent amount of material, but some of it's outdated. E.g., there's a discussion of the InfoGatherer class, but that appears to no longer exist. There's a good amount of info on InfoCollector but not on InfoProvider or InfoManager; to the extent that I find their headers in the public include/ directory and therefore imagine they'll be used by user-developers, it would nice to see them also documented.

Home.md, which is the homepage on the Wiki (as opposed to the README.md) is basically a skeleton, so the good news is we don't need to worry about merging it into README.md and can just get rid of it

The README.md has an unfilled section titled "Building and running examples" which I imagine we'd still want to have written.