Conformance clarification for region name/area types

[RosalynHatcher]

Clarification to conformance document for region names/area_types to allow use of flag_values and flag_meanings as per discussion in #198. This was a PR that got missed before the conformance document was moved into the cf-conventions repository.

See issue #198 for discussion of these changes.

Release checklist

• Authors updated in cf-conventions.adoc?
• Next version in cf-conventions.adoc up to date? Versioning inspired by SemVer.
• history.adoc up to date?
• Conformance document up-to-date?

For maintainers

After the merge remember to delete the source branch.
Tags are set at the conclusion of the annual meeting; until then master always is a draft for the next version.

[davidhassell]

Hi @RosalynHatcher Thanks for this. As this original discussion was concluded and agreed, I don't think we need to wait the usual three weeks before merging this - it's essentially a housekeeping task, now.

Could you make a note of a link to the unmerged PR in the old conformance repo, for the record?

[RosalynHatcher]

Original PR in the conformance repos is cf-convention/Conformance#10