Add "resources" parameter in Kubernetes context

Add "resources" parameter in Kubernetes context

This new parameter, "resources", will allow the user to automatically
add resources in a pod definition per container.

Example of yaml definition in Kubernetes:
apiVersion: v1
kind: Pod
metadata:
  name: frontend
spec:
  containers:
    - name: db
      image: mysql
      resources:
        requests:
          memory: "64Mi"
          cpu: "250m"
        limits:
          memory: "128Mi"
          cpu: "500m"

Example of definition in a Yardstick context:
context:
  type: Kubernetes
    servers:
        host:
            resources:    # There are two possible keys in this dict:
                          # "requests" and "limits".
              limits: <dictionary>
              requests: <dictionary>

Resources in containers [1].

[1] https://kubernetes.io/docs/concepts/configuration/manage-compute-resources-container/

JIRA:YARDSTICK-1171

Change-Id: I163d72d9d3e88b538fca73eb4dbf38613aa23ff4
Signed-off-by: John O Loughlin <john.oloughlin@intel.com>