add a simple plugin system

Pilz.UI.Telerik.SymbolFactory/Extensions.cs

@@ -0,0 +1,25 @@
+using System;
+using System.Collections.Generic;
+using System.Drawing;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using Telerik.WinControls;
+using Telerik.WinControls.Svg;
+
+namespace Pilz.UI.Telerik
+{
+    public static class Extensions
+    {
+        public static Image ToImage(this RadSvgImage svg)
+        {
+            return svg?.Document.Draw(svg.Width, svg.Height);
+        }
+        
+        public static void ApplyColor(this RadSvgImage svg, Color color)
+        {
+            svg.Document.Fill = new SvgColourServer(color);
+            svg.ClearCache();
+        }
+    }
+}

Pilz.UI.Telerik.SymbolFactory/SymbolFactory.cs

@@ -52,10 +52,7 @@ namespace Pilz.UI.Telerik
         public virtual RadSvgImage GetSvgImageColored(TSvgSymbols svgImage, Size size, Color color)
         {
             var img = GetSvgImage(svgImage, size);
-
-            img.Document.Fill = new SvgColourServer(color);
-            img.ClearCache();
-
+            img.ApplyColor(color);
             return img;
         }
 
@@ -81,7 +78,7 @@ namespace Pilz.UI.Telerik
 
         public virtual Image GetImageFromSvg(RadSvgImage svg)
         {
-            return svg.Document.Draw(svg.Width, svg.Height);
+            return svg.ToImage();
         }
     }
 }