Support more validation actions for policy bindings

[f1ames]

In the first version of Monokle Admission Controller, the only validation action supported is Warn (send warning for every policy violation detected).

apiVersion: monokle.io/v1alpha1
kind: MonoklePolicyBinding
metadata:
  name: my-policy-binding
spec:
  policyName: my-policy
  validationActions: [Warn]

We would like to expand this with more options like:

• Ignore - ignore violations.
• Audit - send violation details to Monokle Cloud.
• Deny - block resource creation/update.

Also it could be useful to allow defined action per rule level (so different actions for warnings and errors).

[olensmar]

should we use "Audit" instead of "Report" ? (which i've seen others do..)