Hooks configuration API refactoring

[dmgtn]

We have a few problems in API that should be fixed:

1. First of all – we mistakenly use operation instead of operator in matchExpressions clause. This is a real bug and should be fixed.
2. We use selector, containing matchLabels and matchExpressions fields. But the more Kubernetes-compatible name will be labelSelector. Rename selector to labelSelector.
3. In Add support of matchLabels and matchExpressions for namespaceSelector  #32 we are going to add matchLabels and matchExpressions to namespace. Instead of just adding them to namespaceSelector, we better introduce new field namespace, and then add there labelSelector.
4. Fully abandon namespaceSelector, and instead of it namespace.labelSelector (as already suggested above), namespace.nameSelector (having matchNames).
5. Add support for field selector for onKubernetesEvent hooks #35 and Replace objectName with nameSelector.matchNames #33 also implement in better way.
6. Introduce v1 (Introduce versioning for hooks configuration API #36)

Full example:

{
  "configVersion": "v1",
  "onKubernetesEvent": [
    {
      "name": "Monitor labeled pods in cache tier",
      "kind": "Pod",
      "event": [ "add", "update", "delete" ],
      "nameSelector": {
        "matchNames": ["pod-xxx", "pod-yyy", "pod-zzz"],
      },
      "labelSelector": {
        "matchLabels": {
          "myLabel": "myLabelValue",
          "someKey": "someValue",
          ...
        },
        "matchExpressions": [
          {
            "key": "tier",
            "operator": "In",
            "values": ["cache"],
          },
          ...
        ],
      },
      "fieldSelector": { 
        "matchExpressions": [
          {
            "field": "status.phase",
            "operator": "Equal",
            "value": "Pending",
          },
          ...
        ],
      },
      "namespace": {
        "nameSelector": {
          "matchNames": ["somenamespace", "proj-production", "proj-stage"],
        },
        "labelSelector": {
          "matchLabels": {
            "myLabel": "myLabelValue",
            "someKey": "someValue",
            ...
          },
          "matchExpressions": [
            {
              "key": "tier",
              "operator": "In",
              "values": ["cache"],
            },
            ...
          ]
        }
      },
      "jqFilter": ".metadata.labels",
      "allowFailure": true|false,
    },
  ]
}