message: Add powerShellVersion property to SiteConfig
diff: "description": "Version of Node.js.",
  "type": "string"
  },
  + "powerShellVersion": {
  + "description": "Version of PowerShell.",
  + "type": "string"
  + },
  "linuxFxVersion": {
  "description": "Linux App Framework and version",
  "type": "string"
  