I passed this to the development department, and they came back to me with the news that we don't currently support it as it's not S3 compatible (I think they mean 'similar, but not the same' - anyhow, we don't support it). Some providers, e.g. RackSpace, have cloud storage services that support S3 or Swift (note the differentiation: if it was one and the same thing, they presumably wouldn't list them as alternatives).
It may be added at some point, but no promises or ETA, sorry
It may be added at some point, but no promises or ETA, sorry