anchor.diff:  * Successful operation uses 204 No Content
   * Errors use a non-200 and (optionally) an error payload. See subsection on Error Responses for more details.
   
  -
  -+ Parameters
  -    + entityId: Bcn_Welt (required, string) - Entity ID
  ++ Parameters 
  +    + entityId (required, string) - Entity id to be updated
   
   + Request (application/json)
   
  
positive.code: an opaque way. Nonetheless, the types described below are used to convey an special meaning
  
  * `date`:  identifies dates, in ISO8601 format. These attributes can be used with the
    greater than, lesser than, greater or equal, lesser or equal and range query operators. Eg:
  
  ```
    "timestamp": {
      "value": "2017-06-17T07:21:24.238Z",
      "type: "date"
    }
  ```
  
  * `geo:point`: identifies the location of the entity in geo-location queries. If an entity have several attributes
    of this type all them define a possible location for the entity from a geo-location query point of view. (TBD:
    check feasibility).
  
  ```
    "location": {
      "value": "41.3763726, 2.1864475,14",
      "type": "geo:point"
    }
  ```
  
  ### Canonical format description
  
negative.code: * Errors use a non-200 and (optionally) an error payload. See subsection on Error Responses for more details.
  
  + Parameters
      + entityId (required, string) - Entity id to be updated
      + options (optional, string) - Operations options
          + Members
              + append - Force an append operation
  
  + Request (application/json)
  
  