结构调整，便于后续扩展

AIStudio.Wpf.BaseDiagram/Commands/IActiveAware.cs

@@ -0,0 +1,26 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace AIStudio.Wpf.BaseDiagram.Commands
+{
+    /// <summary>
+    /// Interface that defines if the object instance is active
+    /// and notifies when the activity changes.
+    /// </summary>
+    public interface IActiveAware
+    {
+        /// <summary>
+        /// Gets or sets a value indicating whether the object is active.
+        /// </summary>
+        /// <value><see langword="true" /> if the object is active; otherwise <see langword="false" />.</value>
+        bool IsActive { get; set; }
+
+        /// <summary>
+        /// Notifies that the value for <see cref="IsActive"/> property has changed.
+        /// </summary>
+        event EventHandler IsActiveChanged;
+    }
+}