json-edit: allow key elements containing '.', by backslash-escaping

    ./json-edit -a 'foo.2\.0.bar' -v 'value' test.json

will now result in:

    {
      "foo": {
        "2.0": {
          "bar": "value"
        }
      }
    }

This is now required since we will be enumerating repositories to be
included in autoyast.xml generation from meta-data contained in
provisioner.json, and we want to key that meta-data by repository
name to avoid requiring an extra set of repository keys.  Repository
names can be things like "SUSE-Cloud-2.0-Updates", hence the need for
allowing JSON key elements to contain ".".

There is a corresponding commit in the barclamp-provisioner repository
adding the same behaviour to parse_node_data.
skip local repo checks if external SMT server is configured