ST: Added :copy_via variable to :copy strategy in order to :scp or :sftp (default) to the remote machines

Hi,

I've added the variable :copy_via for the :copy strategy in order to define how to move the tar/zip across to the remote machines. One of my clients does not support :sftp so we're using :scp instead.

Would be nice to have it in the official repo. Many thanks.

Rudi