clarify relationship between requirements 4 and 59

[jyutzler]

We got a question regarding Requirement 4 being untestable because the GeoPackage was determined to be an Extended GeoPackage as described by Requirement 59. We could make the relationship between these requirements more clear.

[jyutzler]

This topic came up again during today's CITE SC meeting.

[jyutzler]

We discussed this again during the March 28 SWG meeting and agreed to relax the Requirement 4. In 2023, GeoPackages aren't particularly viable unless they have at least some extensions. The existence of this requirement, as written, is just confusing people.

The plan is to relax the requirement, specifying the minimum schema for a GeoPackage. We didn't discuss this in the SWG, but in retrospect, I believe it would also be appropriate to indicate that a GeoPackage have at least some content as features, tiles, or attributes. I'll propose it as a warning. We will see how the participants react to that.

This is somewhere in the middle between a substantive change and an administrative change, but since we plan to do a minor revision anyway, the SWG decided to be safe and call it a substantive change.