Update the Euphrates docs for kubernetes scenario

Update the Euphrates docs for kubernetes scenario

JIRA: -

In the Euphrates release, compass has supported kubernates
deployment now. However, there is no k8s related description
in docs of compass4nfv. So we add k8s related description in
this patch including the k8s architeture, k8s networking in
Compass, k8s virtual deployment and k8s bare metel deployment.

Change-Id: I3bea3ae06b1c73076ba44d10caf89602928b7021
Signed-off-by: Yifei Xue <xueyifei@huawei.com>
(cherry picked from commit 4f90858ffbe3e566f30f8bf58309d28989212d0e)