feature: API Start and Stop mechanism for RpaasInstance.

[gvicentin]

This PR is adding two new commands to the rpaasv2 plugin cli and two new routes to the rpaasv2 api for managing the Shutdown state.

1. Start

The start command will scale out RpaasInstance replicas and setup autoscaling objects if needed.

$ ./bin/rpaasv2 start -s some-service -i my-instance
Started instance some-service/my-instance

2. Stop

The stop command will scale in RpaasInstance replicas and remove autoscaling objects if needed.

$ ./bin/rpaasv2 stop -s some-service -i my-instance
Shutting down instance some-service/my-instance

3. Info

The info command now shows information about the Shutdown state.

$ ./bin/rpaasv2 info -s some-service -i my-instance
Name: my-instance
Description:
Tags:
Team owner:
Plan: basic
Flavors:
Shutdown: false
...

4. Extra

Also now, RpaasInstance shutdown's state is showing when using kubectl.

$ kubectl get rpaasinstance
NAME          SUSPENDED   SHUTDOWN   AGE   IPS   HOSTNAMES
my-instance   false       false      10d