Fixes: U4-662 Most icon for document type can't be shown in 4.8.1.

src/Umbraco.Core/IconPickerBehaviour.cs

@@ -0,0 +1,24 @@
+namespace Umbraco.Core
+{
+    public enum IconPickerBehaviour
+    {
+        /// <summary>
+        /// Default umbraco behavior - show duplicates in files and sprites
+        /// </summary>
+        ShowDuplicates,
+
+        /// <summary>
+        /// If a file exists on disk with the same name as one in the sprite
+        /// then the file on disk overrules the one in the sprite, the 
+        /// sprite icon will not be shown
+        /// </summary>
+        HideSpriteDuplicates,
+
+        /// <summary>
+        /// If a file exists on disk with the same name as one in the sprite
+        /// then the file in the sprite overrules the one on disk, the file
+        /// on disk will be shown
+        /// </summary>
+        HideFileDuplicates
+    }
+}