Task/581 v1 context entities attributes value 4ops

### DEscription
New set of convops:
GET/PUT/POST/DELETE /v1/contextEntities/type/{type}/id/{id}/attributes/{attr_name}/{id_value}

Good idea. I'd suggest TechDebt SHOULD type. You can reference #588 from that new issue and even include the code pattern to apply to these cases, i.e:

```
if (response.contextElementResponseVector.size() == 0)
{
  statusCode.fill(SccContextElementNotFound,
  std::string("Entity-Attribute pair: '") + entityId + "-" + attributeName + "'");
}
else if (response.contextElementResponseVector.size() == 1)
{
  ContextElementResponse* cerP = response.contextElementResponseVector.get(0);
  if (response.errorCode.code != SccNone)
  {
    statusCode.fill(&response.errorCode);
  }
  else if (cerP->statusCode.code != SccNone)
  {
    statusCode.fill(&cerP->statusCode);
  }
  else
  {
    statusCode.fill(SccOk);
  }
}
else
{
  statusCode.fill(SccReceiverInternalError,
                          "More than one response from deleteAttributeValueInstanceWithTypeAndId::mongoUpdateContext");
}
```