Add a --delete-prev option to 'ecl queries copy'

Currently you can --delete-prev on an 'ecl publish' command, but cannot do likewise on an 'ecl queries copy' command.

This would be a useful feature for our CI/CD efforts in automating deployments to Roxie clusters, as we currently publish to a single cluster, then copy the published query to all of the remaining clusters.

For all of the clusters copied to, this leaves the prior version of the query inactivated, and to delete it requires an 'unpublish' command for the prior version (which requires one to also determine what the prior version of each query was).

afishbeck svaradarajan chambemx frateslx