DTS file copy process tracker endpoint

[briehl]

The MVP for the DTS file copier automatically moves the files from the DTS staging directory to the user's directory. This is done by a daemon that just watches for file changes and silently moves them.

It's likely that these will be Big directories. There should be a way to monitor what's being copied and how long it can be expected to take.

This should take the form of an endpoint (something like /dts_copy_monitor/<username>) which would return a list of all files being copied, their sizes, and whether they're complete. When the copy process is completed, it should return nothing.