Some of the sections contained multiple Options or Metadata Keys

(or Keys) subsections, divided into Required, Recommended, or Optional

categories.
To keep things a bit cleaner and more consistent, we now have at most

one Options or Metadata Keys per section (with consistent naming),

and mark specific options or keys as required, recommended,

optional, or reserved. This is consistent with how we mark up

sub-keys in the metadata sections, and keeps the spec from seeming too

sprawled out.

Built the docs and read through the affected sections. Checked for any

errors as a result of this change.