anchor.diff:  
   ### Update attribute value [PUT /v2/entities/{entityId}/attrs/{attrName}/value]
   
  -The request payload is the new attribute value. It can be represented as a JSON object (application/json),
  -with a `value` property, or as plain text (text/plain).
  +The request payload is the new attribute value.
  +
  +* If the request payload MIME type is `application/json`, then the value of the attribute is set to the JSON object or array
  +  coded in the payload (if the payload is not a valid JSON document, then an error is returned).
  +* If the request payload MIME type is `text/plain`, then the following algorithm is applied to the payload:
  +  * If the payload starts and ends with citation-marks (`"`), the value is taken as a string (the citation marks themselves are not
  +    considered part of the string)
  +  * If `true` or `false`, the value is taken as a boolean.
  +  * If `null`, the value is taken as null.
  +  * If these first three tests 'fail', the text is interpreted as a number.
  +  * If not a number, then an error is returned and the attribute's value is unchanged.
  +
  +The payload MIME type in request is specified in the `Content-Type` HTTP header.
   
   Response:
   
  
positive.code: + Parameters
      + entityId: Bcn_Welt (required, string) - Entity ID
      + attrName: temperature (required, string) - Attribute to be retrieved.
      + options: (optional, string) - Options dictionary
  
  + Response 200 (application/json)
  
  
negative.code:   "location": {
      "value": "41.3763726, 2.1864475,14",
      "type": "geo:point"
    }
  }
  ```
  