Ability for Group Owners to Delete Groups

[marykatefain]

• Submits kind 5s with a and e tags to the group
• Hides the deleted groups in the UI even if the relay didn't delete them
• Checks to ensure the delete request came from the owner of the group
• Maintains posts from deleted groups, but indicates the original group was deleted
• Warns users that this does not guarantee deletion and does not delete posts within the group

I think this will help with the "junk" spam of people just creating groups for testing or multiple groups on accident. They can delete their own group to clean it up if its junk.