NFT listings for marketplaces

[olanod]

We should create an abstraction for NFTs that allows other components of the system to easily deal with "listings" a way to define items that are priced in any given asset(e.g. stable coins) and have a life cycle with possible hooks.

We expect the system to be suitable for communities listing products and services, items can be purchased with the payments pallet by specifying the instance of the nft on sale.