= Per-user file sandbox =

When using web-based job submission, input files can be large,
and it would be inconvenient to upload these files each time jobs are submitted.
Instead, we allow users to maintain a set of files on the project server;
this is called the user's "file sandbox".

Using a web interface (sandbox.php), users can

 * upload files from PC to sandbox
 * view the files in their sandbox, including size and MD5.
 * download files from sandbox to PC
 * delete files from the sandbox

Files in the sandbox can be modified,
and all old versions are retained on the server.
When a batch of jobs is submitted,
it uses the input file versions at the moment of submission,
even if the files are then modified while the batch is in progress.