`ocm create cluster` should have a json output

sometimes we want to script `ocm create cluster` and I don't want to 
```console
$ OCM_CREATE=$(ocm create cluster ${CLUSTER_NAME})
$ CLUSTER_ID=$(echo $OCM_CREATE | grep '^ID:' | awk '{print $2}')
```
and something along the lines of
```console
$ OCM_CREATE_JSON=$(ocm create cluster ${CLUSTER_NAME} --output=json )
$ CLUSTER_ID=$( echo $OCM_CREATE | jq .id )
```
