Prediction market for a bounty

*Type*: feature

For every contest or cooperative bounty create a prediction market of who will win the prizes.

You can use either the [`ConditionalTokens` contract from Gnosis](https://docs.gnosis.io/conditionaltokens/docs/devguide01/) or [my new contract](https://github.com/vporton/conditional-tokens-contracts/blob/bid-addresses/contracts/BidOnAddresses.sol).

It is useful for:

- stimulating creators to work (and disstimulate very bad creators)
- giving creators some money in advance

It also creates a new way to earn money, as users of GitCoin could trade the conditional tokens.