Add fanout support for NFT membership

[echohtp]

Problem

Wallet membership model is too restrictive. Add support for NFT membership model.

Allow creator to choose what model they want

Solution

Add support for MembershipModel.NFT

To achieve this we need a list of NFT mint hashes to which we assign a share to

This list can be user supplied in lieu of args.members as args.nfts

If args.nfts is not supplied we mint NFT's which we ultimately send to the members wallet.

to mint nfts we need

• an image asset (auto generate an image with descriptive text, or something stock we can use)
• metadata json