message: schema: Add message list to DeviceAdded/DeviceList
  A client should be able to know what messages a server exposes for a
  device. This allows us to attach that list whenever a device is
  connected to the server.
  Fixes
diff: "Id"
  ]
  },
  + "DeviceMessages" : {
  + "description": "A list of the messages a device will accept on this server implementation.",
  + "type": "array",
  + "items" : {
  + "type": "string",
  + "minItems": 1
  + }
  + },
  "SystemIdMessage" : {
  "description": "Message sent by the server that is not in direct reply to a message send from the client, and always uses system Id.",
  "properties": {
  "items": {
  "properties": {
  "DeviceName": { "$ref" : "#/components/DeviceName" },
  - "DeviceIndex": { "$ref" : "#/components/DeviceIndex" }
  + "DeviceIndex": { "$ref" : "#/components/DeviceIndex" },
  + "DeviceMessages": { "$ref" : "#/components/DeviceMessages" }
  },
  - "minProperties": 2,
  - "maxProperties": 2,
  + "minProperties": 3,
  + "maxProperties": 3,
  + "additionalProperties": false,
  "required": [
  "DeviceName",
  - "DeviceIndex"
  - ],
  - "additionalProperties": false
  + "DeviceIndex",
  + "DeviceMessages"
  + ]
  }
  }
  },
  "properties": {
  "Id": {"$ref": "#/components/SystemId"},
  "DeviceName": { "$ref" : "#/components/DeviceName" },
  - "DeviceIndex": { "$ref" : "#/components/DeviceIndex" }
  + "DeviceIndex": { "$ref" : "#/components/DeviceIndex" },
  + "DeviceMessages": { "$ref" : "#/components/DeviceMessages" }
  },
  - "minProperties": 3,
  - "maxProperties": 3,
  + "minProperties": 4,
  + "maxProperties": 4,
  "additionalProperties": false,
  "required": [
  "Id",
  "DeviceName",
  - "DeviceIndex"
  + "DeviceIndex",
  + "DeviceMessages"
  ]
  },
  "DeviceRemoved": {
  