added dialog popup on extraction errors.

looks like Ookii.Dialogs have to be replaced with manual progress dialog
implementation, as i have no control over progress dialog window once
extraction has begun.

frankly, i just need to be able to call StopProgressDialog and
StartProgressDialog from IProgressDialog interface, but Ookii does not
provide such low-level access.

GUI/FileErrorDialog.xaml.cs

@@ -0,0 +1,76 @@
+using System;
+using System.Windows;
+using System.Windows.Controls;
+using System.Windows.Input;
+
+namespace GARbro.GUI
+{
+    /// <summary>
+    /// Interaction logic for FileErrorDialog.xaml
+    /// </summary>
+    public partial class FileErrorDialog : Rnd.Windows.ModalWindow
+    {
+        public FileErrorDialog (string title, string error_text)
+        {
+            InitializeComponent();
+            this.DataContext = new ViewModel { Title = title, Text = error_text };
+        }
+
+        private void ContinueButton_Click (object sender, RoutedEventArgs e)
+        {
+            this.DialogResult = true;
+        }
+
+        private void AbortButton_Click (object sender, RoutedEventArgs e)
+        {
+            this.DialogResult = false;
+        }
+
+        private class ViewModel
+        {
+            public string         Title { get; set; }
+            public string          Text { get; set; }
+            public ICommand CopyCommand { get; private set; }
+
+            public ViewModel ()
+            {
+                CopyCommand = new ActionCommand (CopyText);
+            }
+
+            private void CopyText ()
+            {
+                try
+                {
+                    Clipboard.SetText (Text);
+                }
+                catch (Exception X)
+                {
+                    System.Diagnostics.Trace.WriteLine (X.Message, "Clipboard error");
+                }
+            }
+        }
+
+        private class ActionCommand : ICommand
+        {
+            readonly Action     m_action;
+
+            public ActionCommand (Action action)
+            {
+                m_action = action;
+            }
+
+            public void Execute (object parameter)
+            {
+                m_action();
+            }
+
+            public bool CanExecute (object parameter)
+            {
+                return true;
+            }
+
+            #pragma warning disable 67
+            public event EventHandler CanExecuteChanged;
+        }
+    }
+}