call $pseudoRequest->uploadFiles with a list of filenames, it will populate
the upload method with upload objects, so that Storage->getFileFromFormPost
will have an object with all the right methods.
t/Storage.t tests this incidently. It occurs to me that we need tests
for our PseudoRequest module, and it needs POD, and it should probably
be rewritten using Class::InsideOut for good form.