anchor.diff:  * subscriptions to deal with subscriptions to context changes
   * registrations to deal with context data by registering external providers
   
  -## Retrieve the Entry Point [GET]
  +### Retrieve entry points [GET /v2]
   
   + Response 200 (application/json)
   
  
positive.code:          }
          ]
  
  ### List all entities of an specific type [GET /v2/entities{?type}]
  
  + Parameters
      + type: Room (optional, string) - Only retrieve entities of this type
  
  + Response 200 (application/json)
  
          [
  
negative.code:             "temperature": 35.6
           },
           {
              "type": "Car",
              "id": "abc345fg",
              "speed": 14.7
           }
          ]
  
  ### Pagination [GET /v2/entities{?limit,offset,options}]
  
  + Parameters
      + options: count
      + limit: 2
      + offset: 2
  
  + Response 200 (application/json)
  
      + Headers
  
              X-Total-Count: 30
              Link: http://context.example.org/v2/entities?offset=4&limit=2; rel="next", http://context.example.org/v2/entities?offset=28&limit=2; rel="last", http://context.example.org/v2/entities?offset=0&limit=2; rel="first", http://context.example.org/v2/entities?offset=2&limit=2; rel="prev"
  
      + Body
  
        [
           {
              "type": "Room",
              "id": "DC_S1_D41",
              "temperature": {
                 "value": 35.6,
                 "type": "urn:ogc:def:phenomenon:temperature",
                 "metadata": {
                     "accuracy": {
                         "type": null,
                         "value": "0.1"
                     }
                 }
              }
           },
           {
              "type": "Car",
              "id": "abc345fg",
              "speed": {
                  "value": 14.7,
                  "type": null,
                  "metadata": { }
              }
           }
        ]
  
  
  ## Filter entities [/v2/entities{?id}]
  
  ### By id [GET /v2/entities{?id,options}]
  
  + Parameters
      + id: DC_S1_D41 (optional, string) - Only retrieve entities with this id
      + options: keyValues (optional, string) - rendering options
  
  + Response 200 (application/json)
  
  