ralsh: allow dealing with multiple resources

[lutter]

Right now, ralsh only operates on one resource. It should also be able to operate on multiple resources, e.g.

ralsh package kernel glibc augeas

to list multiple packages, and

ralsh service httpd ensure=running smartd ensure=stopped docker ensure=running enable=true

to modify multiple resources in one go.

This mainly has repercussions for the output, both plain text and the JSON output.