Add Qos Model to Dataclay

[fcarp10]

Java class as reference for the qosmodel resource in dataclay:

https://github.com/mF2C/ServiceManagement/blob/master/src/main/java/sm/elements/QosModel.java

[dgasull]

Implemented in PR mF2C/mF2C#141 . Working json example:

{
"id": "qos-model/qos-model",
"service": { "href": "service/service" },
"agreement": { "href": "agreement/agreement" } ,
"agents": [ { "href": "agent/agent" } ],
"config": "qos config",
"num_service_instances": 2,
"num_service_failures": 3,
"current_state": [1.0, 3.5],
"next_state": [1.0]

}

@fcarp10 Please confirm, everything is OK!