Add Env.VersionString

Author: mythz

src/ServiceStack.Text/Env.cs

@@ -47,9 +47,13 @@ static Env()
                 + platformName
                 + (IsMono ? "/Mono" : "/.NET");
 
+            VersionString = ServiceStackVersion.ToString();
+
             __releaseDate = DateTime.Parse("2001-01-01");
         }
 
+        public static string VersionString { get; set; }
+
         public static decimal ServiceStackVersion = 4.00m;
 
         public static bool IsUnix { get; set; }