Better writing on NVD API key for DependencyCheck

[binkley]

While eating our own dogfood, I'm using the directions in the wiki to add NVD API key when speeding up builds.
I'm using https://github.com/binkley/kotlin-magic-bus as a guinea pig to validate following what we say about "Shifting security left", and providing quickly usable instructions.

Tasks

• Better copy/paste instructions for source config files
• Better discussion on tooling to export unshared secrets to builds, including CI