Get docs in sync with current feature set

[zachrybaker]

There's several places where docs seem stale.

It would be really helpful if the documents described how to update the NVD binary db without scanning any project, from the CLI.

This would allow folks using this on a build server to not burden a project build with having to do this.

[digitalcoyote]

I'm actually working on that now, but running the update command through NuGetDefense seems to break often enough it's an issue. For anyone needing to do this now, the NuGetDefense.NVD project has a feed importer I previously used to build the local NVD data.

nugetdefense Recreate-NVD and nugetdefense Update-NVD should be usable and documented once that is fixed

[digitalcoyote]

I have a fix for the Recreate-NVD command so I added a small explanation and exampel for it. I'm going to start retesting the Update command next and then add more relevant documentation for it.