manifests syntax issues - validate analyzer warning/error

[shireenf-ibm]

• raise warning/error when input yaml file has no "---" separator between the resources
  (found an example with such input, for which some of the resources were just ignored instead of having warn/err issued, and then the output did not match the expected, when one assumes all the resources are considered for the analysis) .

• raise a warning/ error when the manifests are using selectors with wrong fields;
  example :
  following input rule-peer in an ANP :

 action: "Allow"
     from:
     - namespaces:
         namespaceSelector:
           matchLabels:
             kubernetes.io/metadata.name: monitoring

is not correct as the namespaces is of type *metav1.LabelSelector and the namespaceSelector is not needed;
this input causes wrong parse result of the namespaces field; however no warning/ error is returned