mask server side

[jovo]

it would be great to have a service such that when we upload a brain mask, server side that mask is propagated both up & down zoom levels, and applied, which automatically builds a new image token that is the same as the original one but appended with '_mask', or some such

[randalburns]

ok, this is easy. We alread have this kind of thing. That being said, I won't write it until I have a real example and dataset. Doesn't have to be big. Just make it concrete.