DataExtension Group API implementation

[AuroraLS3]

I would like to be able to..

See more metadata about different DataExtension groups.

Is your feature request related to a problem? Please describe.

DataExtension API has Group which allows giving data about a specific group, but it has not been implemented.

Example: Towny: List of towns, each town has:

• Mayor
• List of residents
• Claimed chunks
• Maximum claim chunks
• Creation date
• Bank account (funds)
• Fees (That reduce funds)
• Rent (That increase funds)
• Nation (optional)

This data is currently not visible in Plan even though it would be useful for servers to follow what is going on.

Split from #1769