introduce GuaranteeAllocation and GuaranteeOutcome

[geoknee]

These TS types will be useful in constructing arguments to supply to the forthcoming claim function.

That function should have a signature something along the lines of:

    /**
     * @dev Computes the new outcome that should be stored against a target channel after a claim is made on its guarantor.
     * @param initialGuaranteeOutcome the outcome containing at least one guarantee(s) which will be claimed for each asset.
     * @param initialHoldings initial quantity of each asset held on chain for the guarantor channel. Order matches that of initialGuaranteeOutcome.
     * @param targetChannel the index of the guarantee in the list of guarantees for the given asset -- equivalent to declaring a target channel
     * @param targetOutcome initial outcome stored on chain for the target channel.
     * @param indices list of list of indices expressing which destinations in the allocation should be paid out for each asset.

     */
    function claim(
        ExitFormat.SingleAssetExit[] memory initialGuaranteeOutcome,
        uint256[] memory initialHoldings,
        uint48 targetChannel,
        ExitFormat.SingleAssetExit[] memory initialTargetOutcome,
        uint48[][] memory exitRequest
    )
        public
        pure
        returns (
            ExitFormat.SingleAssetExit[] memory updatedTargetOutcome,
            uint256[] memory updatedHoldings,
            ExitFormat.SingleAssetExit[] memory exit
        )

The method should revert if:

• the guarantee is not of the correct format (e.g. does not use the magic constant)

• exit-format/ts/nitro-types.ts

  Lines 5 to 6 in 81a99f5

  	export const MAGIC_VALUE_DENOTING_A_GUARANTEE =
  	"0x0000000000000000000000000000000000000001";

• the targetOutcome is not of the correct format (e.g. does use the magic constant)

[geoknee]

in favour of #13