Specify unobserveproperty operation

[benfrancis]

5.2.2.8 MUST define a way for a WoT Consumer to stop observing a property of a Web Thing so that it no longer gets notified when the value of the property changes

[benfrancis]

Proposal from #42

Request

{
  "thingID": "https://mythingserver.com/things/mylamp1",
  "messageID": "c370da58-69ae-4e83-bb5a-ac6cfb2fed54",
  "messageType": "request",
  "operation": "unobserveproperty",
  "name": "on",
  "correlationID": "5afb752f-8be0-4a3c-8108-1327a6009cbd"
}

Response

{
  "thingID": "https://mythingserver.com/things/mylamp1",
  "messageID": "79057736-3e0e-4dc3-b139-a33051901ee2",
  "messageType": "response",
  "operation": "unobserveproperty",
  "name": "on",
  "correlationID": "5afb752f-8be0-4a3c-8108-1327a6009cbd"
}