Allow upload of def files directly to Sets Manager

[dlglin]

I think we've discussed this before, but we should consider an interface where set definition files can be uploaded directly to the Sets Manager (and .lst files to the Accounts Manager). Instead of uploading via the file manager and then importing via the Manager page this could all be done in one step.

The Accounts/Sets Manager could give the user the option of importing from a file in the course directory or from their computer.