Default times of copyitems to 1

[Nic-Ma]

Is your feature request related to a problem? Please describe.
Feature request from @holgerroth : why not default to times=1 in CopyItemsd? Seems copying one time would be the most common usage. https://github.com/Project-MONAI/MONAI/blob/dev/monai/transforms/utility/dictionary.py#L861