Concurrent ASA-to-ASA swaps

[cusma]

Issue
Since the ASA-to-ASA swap requires the offered ASA to be deposited in the Swapper Contract, there is a limitation for those users willing to concurrently swap a card for different possible requested cards.

Example
Let's say a user offers card A accepting either cards B, C or D as possible requested ASA. Since user has just 1 card A is not possible to open multiple requests for card B, C or D at the same time, since the user can only deposit A in one Swapper Contract at time.

Proposal
Adding an Or condition on requested ASA, so that the Swapper Contract could approve concurrent swaps with B, C or D at the same time, in the same Swapper Contract.