Fix suffixes converter, part 1

1. fix #568, fix #566 fix #553, fix #559
2. simple refactoring

Plugins/Wox.Plugin.Program/SuffixesConverter.cs

@@ -0,0 +1,33 @@
+using System;
+using System.Globalization;
+using System.Windows.Data;
+using System.Windows.Markup;
+
+namespace Wox.Plugin.Program
+{
+    public class SuffixesConvert : MarkupExtension, IValueConverter
+    {
+        public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
+        {
+            var text = value as string[];
+            if (text != null)
+            {
+                return string.Join("", text);
+            }
+            else
+            {
+                return string.Empty;
+            }
+        }
+
+        public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
+        {
+            throw new NotSupportedException();
+        }
+
+        public override object ProvideValue(IServiceProvider serviceProvider)
+        {
+            return this;
+        }
+    }
+}