Plugins - Added removal of plugins

Plugins - Added updating plugins at runtime

src/Artemis.Core/Services/Interfaces/IPluginManagementService.cs

@@ -70,6 +70,12 @@ namespace Artemis.Core.Services
         /// <returns>The resulting plugin</returns>
         Plugin ImportPlugin(string fileName);
 
+        /// <summary>
+        /// Unloads and permanently removes the provided plugin
+        /// </summary>
+        /// <param name="plugin">The plugin to remove</param>
+        void RemovePlugin(Plugin plugin);
+
         /// <summary>
         ///     Enables the provided plugin feature
         /// </summary>