Update: Logging guide once swift-log is adopted

[helenmasters]

The page below will need redesigning/augmenting once swift-log support is tagged in a release:
[ ] https://www.kitura.io/docs/logging/helium-logger.html

[helenmasters]

I think what we need to do here is:

• remove the Helium Logger page and instead have something like "Configuring Logging" which needs to point out that we have both LoggerAPI and swift-log but that LoggerAPI is available for historical reasons and that we would expect users to be using swift-log going forward. However, we don't currently have a guide describing LoggerAPI so I think this needs to be a new page.
• HeliumLogger can be a single sentence or two on that page.
• we also need to add in words to cover that HeliumLogger 1.9.0 has just been tagged. This adds the ability to use HeliumLogger as a logging destination (backend) for swift-log (thanks to @will Lisac!)
  https://github.com/IBM-Swift/HeliumLogger/releases/tag/1.9.0