Resume halted uploads/downloads

[beatgammit]

When an upload is halted, it should be resumable. Suppose that I have a huge file that I want to upload (like 3 GB), but I also have crazy annoying latency problems. It would take me forever to try to upload it if I had to keep retrying.

When an upload or download is interrupted, the location in the stream should be stored, and when the connection is resumed it should continue to stream the data where it left off.