title: Open Bluetooth settings programmatically from UIAlertController
body: <p>As titled, the question is how can I open bluetooth settings programmatically from my App? 
  I checked all answers on stackoverflow and not even one is working fine with iOS 11. All of them are old answers for is below 11 or are left without answer. All I can make is take me to general settings or app settings, but I want user to be taken directly to Bluetooth settings, so he can turn it on.</p>
  
  <pre><code>let alert = UIAlertController(title: "Bluetooth is off", message: "Please turn on your bluetooth", preferredStyle: UIAlertControllerStyle.alert)
              alert.addAction(UIAlertAction(title: "Go to settings", style: UIAlertActionStyle.default, handler: { (action) in
                  switch action.style {
                  case .default:
                      let url = URL(string: "App-Prefs:root=Bluetooth") //for bluetooth setting
                      let app = UIApplication.shared
                      app.openURL(url!)
                      print("default")
                  case .cancel:
                      print("cancel")
                  case .destructive:
                      print("destrucive")
                  }
  </code></pre>
  
  <p>What I tried more, also without result:</p>
  
  <pre><code>UIApplication.shared.openURL(NSURL(string: "prefs:root=General&amp;path=Bluetoth")! as URL)
  </code></pre>
  
  <p>Or: </p>
  
  <pre><code>let url = URL(string: "App-Prefs:root=Bluetooth")
  </code></pre>
  
  <p>All above is not working</p>