Work out mechanism for adding/registering new collectables with the stewart

[JasoonS]

The current method of doing this is quite ugly in the constructor.

This should be designed to be flexible, so that when we get to implementing a multi ERC721 contract solution this will still work in a similar way.

This function should also check that the token is able to be a harberger token (ie the modifications to the ERC721 token need to be there). Maybe this isn't necessary for the first version.

A slight tangent
Maybe you can even allow temporary harberger tokens that people can convert back at any time. [eg the owner of the token can call the setApprovalForAll() to false at any time, and to buy the token you need to first set it to true]
There would need to be a strong incentive for people to convert a token into a patronage token in the firstplace, but the design should include this possibility in my opinion. And I can think of a couple of cool ideas where 'time held', or 'time as patronage token' matter, as incentive for people to keep the tokens as harberger tokens.