CEP: Added custom columns on list
CEP: Added custom columns on list

On CEP the default list is not enough for a quick view and it does not
provide a lot of information to the users.

Kubernetes 1.11 added a new option to have custom list on the Custom
Resources definition, so the list provides to the users more
information.

This commit change the CEP list output to the following:

- Kubernetes 1.11
```
vagrant@k8s1:~$ kubectl get cep --all-namespaces
NAMESPACE     NAME                      ENDPOINT ID   IDENTITY ID  POLICY ENFORCEMENT   ENDPOINT STATE   IPV4          IPV6
default       app1-5d79fbc474-fkvxq     24637         37263        none                 ready            10.10.0.54    f00d::a0a:0:0:603d
default       app1-5d79fbc474-n4g2f     17467         37263        none                 ready            10.10.0.247   f00d::a0a:0:0:443b
default       app2-56fbc4b964-gwp6j     9386          22676        none                 ready            10.10.0.39    f00d::a0a:0:0:24aa
default       app3-5d9895d6ff-cwj2q     46066         11397        none                 ready            10.10.0.3     f00d::a0a:0:0:b3f2
kube-system   coredns-b9476b976-zkp9x   54975         30138        none                 ready            10.10.0.220   f00d::a0a:0:0:d6bf
```

- Kubernetes 1.7
```
vagrant@k8s1:~$ kubectl get pods
NAME                    READY     STATUS    RESTARTS   AGE
app1-1879020049-2sb9c   1/1       Running   0          1m
app1-1879020049-vb1z9   1/1       Running   0          1m
app2-2809035625-htqm4   1/1       Running   0          1m
app3-753781860-f1wj9    1/1       Running   0          1m
vagrant@k8s1:~$ kubectl get nodes
NAME      STATUS    AGE       VERSION
k8s1      Ready     12m       v1.7.15
vagrant@k8s1:~$ kubectl get cep
NAME                    KIND
app1-1879020049-2sb9c   CiliumEndpoint.v2.cilium.io
app1-1879020049-vb1z9   CiliumEndpoint.v2.cilium.io
app2-2809035625-htqm4   CiliumEndpoint.v2.cilium.io
app3-753781860-f1wj9    CiliumEndpoint.v2.cilium.io
```

Related to #3334

Signed-off-by: Eloy Coto <2a8acc28452926ceac4d9db555411743254cf5f9@gmail.com>

tgraf/cilium,cilium/cilium,michi-covalent/cilium,tgraf/cilium,michi-covalent/cilium,michi-covalent/cilium,michi-covalent/cilium,tklauser/cilium,scanf/cilium,scanf/cilium,tklauser/cilium,tgraf/cilium,scanf/cilium,cilium-team/cilium,scanf/cilium,scanf/cilium,cilium/cilium,scanf/cilium,tgraf/cilium,tklauser/cilium,michi-covalent/cilium,cilium/cilium,tgraf/cilium,tklauser/cilium,cilium/cilium,tgraf/cilium,cilium/cilium,scanf/cilium,cilium-team/cilium,tklauser/cilium