add a simple plugin system

Pilz.Plugins.Advanced/PluginFunctionParameter.cs

@@ -0,0 +1,12 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Pilz.Plugins.Advanced
+{
+    public class PluginFunctionParameter
+    {
+    }
+}