Wpf: Focus the family text box when showing the FontDialog

Also select all when the size or font family is focused so it is easier to find other fonts.

src/Eto.Wpf/CustomControls/FontDialog/fontchooser.xaml.cs

@@ -226,6 +226,12 @@ void FontChooser_Loaded (object sender, RoutedEventArgs e)
 			// Schedule background updates.
 			_populated = true;
 			ScheduleUpdate ();
+
+			// Make using the keyboard easier by setting focus initially and selecting all
+			sizeTextBox.GotFocus += (sender, e) => sizeTextBox.SelectAll();
+			fontFamilyTextBox.GotFocus += (sender, e) => fontFamilyTextBox.SelectAll();
+
+			fontFamilyTextBox.Focus();
 		}
 
         #endregion