Added plugin unloading

src/Artemis.Core/Plugins/Interfaces/IPlugin.cs

@@ -2,14 +2,21 @@
 
 namespace Artemis.Core.Plugins.Interfaces
 {
+    /// <inheritdoc />
     /// <summary>
     ///     This is the base plugin type, use the other interfaces such as IModule to create plugins
     /// </summary>
     public interface IPlugin : IDisposable
     {
         /// <summary>
-        ///     Called when the plugin is loaded
+        ///     Called when the plugin is activated
         /// </summary>
         void EnablePlugin();
+
+
+        /// <summary>
+        ///     Called when the plugin is deactivated
+        /// </summary>
+        void DisablePlugin();
     }
 }