add a simple plugin system

Pilz.Plugins/PluginStatus.cs

@@ -0,0 +1,18 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Pilz.Plugins
+{
+    public enum PluginStatus
+    {
+        None,
+        Success,
+        FileNotFound,
+        ErrorAtLoading,
+        ErrorAtInitializing,
+        NoValidPlugin
+    }
+}