[BUG] Kubernetes v1.16 incompatibility

[palexster]

Describe the bug

As found by Aldo, Kubernetes v1.16 dropped the legacy support for:
apiVersion extensions/v1beta1
in favor of:
apiVersion: apps/v1

This breaks the Polycube CNI installation, resulting in a kubernetes failure, as the current plugin declares the compatibility with the old API and cannot be installed in K8s 1.16 and onwards.

To Reproduce

Trying to apply polycube CNI manifest, we get:

error: unable to recognize "https://raw.githubusercontent.com/polycube-network/polycube/master/src/components/k8s/standalone_etcd.yaml": no matches for kind "Deployment" in version "extensions/v1beta1"

Additional context

The apiVersion change is documented here: https://kubernetes.io/docs/concepts/workloads/controllers/deployment/

[asimpleidea]

I have grep-ed all the files that contain the unsupported apiVersion and replaced with the new one.
I'll make a PR when I have finished building the docker and tested it with k8s 1.16.

[alacuku]

I already have a working version of the three configuration files: pcn-k8s.yaml, standalone_etcd.yaml and echoserver_nodeport.yaml. Should I make a pull request or we wait for the Elis' fix?

[frisso]

Is Elis fix ok? If so, we can simply accept his fix and merge.

[frisso]

Closed with #214