[TIMOB-26103] iOS 12: Support grouped notifications

   var win = Ti.UI.createWindow({
       backgroundColor: '#fff'
   });
   
   var btn = Ti.UI.createButton({
       title: 'Schedule Notification'
   });
   
   btn.addEventListener('click', function() {
       schedule('id_1', 'New Notification', 'Hey there!', new Date().getTime() + 3000);
       schedule('id_2', 'Another Notification', 'Aloooah!', new Date().getTime() + 4000);
       schedule('id_3', 'Anooooother Notification', 'Hola!', new Date().getTime() + 5000);
       schedule('id_4', 'One more okay?', 'Hello!', new Date().getTime() + 6000);
       schedule('id_5', 'This is the last one', 'Hallo!', new Date().getTime() + 7000);
   });
   
   win.add(btn);
   win.open();
   
   var acceptAction = Ti.App.iOS.createUserNotificationAction({
       identifier: 'ACCEPT_IDENTIFIER',
       title: 'Accept',
       activationMode: Ti.App.iOS.USER_NOTIFICATION_ACTIVATION_MODE_FOREGROUND,
       destructive: false,
       authenticationRequired: true
   });
     
   // An action that does not open the app (background action)
   var rejectAction = Ti.App.iOS.createUserNotificationAction({
       identifier: 'REJECT_IDENTIFIER',
       title: 'Reject',
       activationMode: Ti.App.iOS.USER_NOTIFICATION_ACTIVATION_MODE_BACKGROUND,
       destructive: true,
       authenticationRequired: false
   });
     
    // An action that does not open the app (background action), but lets the developer
   // type in a text (iOS 9+)
   var respondAction = Ti.App.iOS.createUserNotificationAction({
       identifier: 'RESPOND_IDENTIFIER',
       title: 'Respond',
       activationMode: Ti.App.iOS.USER_NOTIFICATION_ACTIVATION_MODE_BACKGROUND,
       behavior: Ti.App.iOS.USER_NOTIFICATION_BEHAVIOR_TEXTINPUT, // or: Ti.App.iOS.USER_NOTIFICATION_BEHAVIOR_DEFAULT,
       authenticationRequired: false
   });
     
   // Create an example notification category
   var downloadContent = Ti.App.iOS.createUserNotificationCategory({
       identifier: 'DOWNLOAD_CONTENT',
       actionsForDefaultContext: [acceptAction, rejectAction, respondAction]
   });
   
   // Register for user notifications and categories
   Ti.App.iOS.registerUserNotificationSettings({
       types: [
           Ti.App.iOS.USER_NOTIFICATION_TYPE_ALERT
       ],
       categories: [downloadContent]
   });
     
   // Monitor notifications received while app is in the background
   Ti.App.iOS.addEventListener('localnotificationaction', function(e) {
       alert('event: localnotificationaction');
   });
   
   // Validate notification settings
   Ti.App.iOS.addEventListener('usernotificationsettings', function(e) {
       Ti.API.info('event: usernotificationsettings');
   })
   
   // Monitor notifications received while app is in the foreground
   Ti.App.iOS.addEventListener('notification', function(e) {
       alert('event: notification');
   });
   
   function schedule(identifier, title, body, date) {
       Ti.App.iOS.scheduleLocalNotification({
           identifier: identifier,
           alertTitle: title,
           alertBody: body,
           summaryArgument: 'My Summary',
           summaryArgumentCount: 2,
           threadIdentifier: 'my_thread',
           date: date,
           category: 'DOWNLOAD_CONTENT'
       });
   }
   

   APPC Studio:  5.1.0.201808080937
   APPC CLI: 7.0.6-Master.5
   iphone 6 simulator (12.0)
   Operating System Name: Mac OS High Sierra
   Operating System Version: 10.13.6
   Node.js Version: 8.9.1
   Xcode 10.0 beta 6