add manual download handler

Wabbajack/Downloaders/ManualDownloader.cs

@@ -0,0 +1,47 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using Wabbajack.Common;
+using Wabbajack.Validation;
+
+namespace Wabbajack.Downloaders
+{
+    class ManualDownloader : IDownloader
+    {
+        public AbstractDownloadState GetDownloaderState(dynamic archive_ini)
+        {
+            var url = archive_ini?.General?.manualURL;
+            return url != null ? new State { Url = url} : null;
+        }
+
+        public void Prepare()
+        {
+        }
+
+        public class State : AbstractDownloadState
+        {
+            public string Url { get; set; }
+            public override bool IsWhitelisted(ServerWhitelist whitelist)
+            {
+                return true;
+            }
+
+            public override void Download(Archive a, string destination)
+            {
+                Utils.Log($"You must manually visit {Url} and download {a.Name} file by hand.");
+            }
+
+            public override bool Verify()
+            {
+                return true;
+            }
+
+            public override IDownloader GetDownloader()
+            {
+                return DownloadDispatcher.GetInstance<ManualDownloader>();
+            }
+        }
+    }
+}