plotman could pause copying when there is another process already copying

[braveckin]

Currently when there is another process finished and plotman starts copying to final destination and other process finishes sooner than the first one finishes copying, the second process starts copy and it slows down both copy processes significantly (on USB hub). Would be nice to have such a flag in config to allow waiting or suspending of process and then unsuspending it after the first process finishes the copy....