[Meta Issue] Documentation cleanup

[webron]

As we work on the spec, we may end up not updating all parts of it completely and before release we need to clean it out. This issue will be used to track known required changes. @OAI/tdc - please edit the this main comment rather than adding requirements as additional comments. Comments added to the ticket will be moved to the main comment and deleted for easier tracking as well.

• added host section #646 introduced a new host construct that should be used for added changes to include host, basePath, schemes #604 as well.
• Addressed metadata documentation cleanup from #589 #812 - new servers should be updated instead of hosts for POI``operation.
• Addressed metadata documentation cleanup from #589 #812 - need an explanation of what happens when scheme/host/basepath are missing.
• Security definition documentation updates #818 - define relative URL behavior across the spec (question came up from relative security urls).
• Added bearer/JWT support and OpenIdConnect #807 - look into renaming apiKey to a more meaningful name.

[MikeRalphson]

Closing as all of the above were merged.