tighten up media type params

[catkins-miso]

• add examples and update media types in paths for limit-type on all slim formats
  • seasonal slim proposal
  • RT slim proposal
  • forecast slim proposal
  • forecast slim snapshot
  • RT slim snapshot
• define canonical names for all limit-types in the spec description limit.yaml
• add include-psr-header examples and update media types for all snapshot
  • forecast detailed
  • forecast normal
  • RT detailed
  • RT normal
  • seasonal detailed
• add inputs-used examples and update media types for slim proposals and snapshots (see optional inputs for slim proposals and snapshots #197)
  • forecast slim proposal: add named example
  • forecast slim snapshot: add media type with an example
  • RT slim proposal: add named example
  • RT slim snapshot: add media type with an example

[catkins-miso]

This would be more appropriate implemented as a media type parameter, I think, since it doesn't change the resource, just elides names from the particular representation. If you are good with that, @getorymckeag, I will change this issue to update each of the media types we've parameterized including this one.

application/vnd.trolie.forecast-limits-snapshot.v1+json; names-header=false:
  schema: ...
  example:
    $ref: '../../example-narratives/examples/forecast-limits-active-power-names-header-elided.json'

I believe that means added an entry like these with good examples for the limit-type parameter we added for slim proposals and snapshot as well as the inputs-used parameter. I also think this deserves its own article to address:

• limit-type is not optional / missing behavior is unspecified
• inputs-used is assumed to be false unless specified. This would be clear from the differences in the examples
• names-header is assumed to be true unless specified.