Adds back in the plugin interfaces. Modifies PluginLoader to try new inteface method for custom plugins first, then fail back to legacy method

essentials-framework/Essentials Core/PepperDashEssentialsBase/Plugins/IPluginDeviceConfig.cs

@@ -3,9 +3,13 @@ using PepperDash.Essentials.Core.Config;
 
 namespace PepperDash.Essentials.Core.Plugins
 {
+    /// <summary>
+    /// Defines a class that is capable of loading custom plugin device types
+    /// </summary>
     public interface IPluginDeviceConfig
     {
         string MinimumEssentialsFrameworkVersion { get; }
+        void LoadPlugin();
         IKeyed BuildDevice(DeviceConfig dc);
     }
 }