Introducing ReplaceFirst() as string extension instead of using the CDF one

src/Umbraco.Core/StringExtensions.cs

@@ -938,7 +938,22 @@ namespace Umbraco.Core
             return text;
         }
 
+        /// <summary>
+        /// Returns a new string in which only the first occurrence of a specified string is replaced by a specified replacement string.
+        /// </summary>
+        /// <param name="text">The string to filter.</param>
+        /// <param name="search">The string to replace.</param>
+        /// <param name="replace">The replacement string.</param>
+        /// <returns>The filtered string.</returns>
+        public static string ReplaceFirst(this string text, string search, string replace)
+        {
+            var pos = text.IndexOf(search);
 
+            if (pos < 0)
+                return text;
+
+            return text.Substring(0, pos) + replace + text.Substring(pos + search.Length);
+        }