Display metrics

[brmzkw]

The control panel can display metrics (CPU usage, memory usage, ...). We should add this support for the CLI too.

[lukaszo]

When working on it, please use samples fields as values are deprecated:

"GetMetricsReply.Metric": {
      "type": "object",
      "properties": {
        "labels": {
          "type": "object",
          "additionalProperties": {
            "type": "string"
          }
        },
        "values": {
          "type": "array",
          "items": {
            "type": "array",
            "items": {
              "type": [
                "string",
                "number"
              ]
            }
          }
        },
        "samples": {  // <---- Use this
          "type": "array",
          "items": {
            "$ref": "#/definitions/Sample"
          }
        }
      }