Add option to the Transfer Tool stop packaging accounts while waiting on others to restore.

As an administrator, I would like the option to limit the accounts that are waiting to be restored on the destination server, in order to minimize the time between creating the cpmove file and making the account live.

At the moment, even with the "Express Transfer" option set, accounts towards the bottom of the Transfer List queue can have hours of downtime from when the cpmove file was created on source and actually restored to the destination, because they're packaged much quicker than the restores can finish.

Ideally, an option to limit the amount of cpmove files waiting to transfer can be added to the "Advanced Options" of the Transfer Tool, so that there's less of a wait from when the account is packaged compared to when it's moved.