Added set for HttpRequestMessageConfiguration.Properties, otherwise a…

…ll have to be copied manually.

[release]

Dapplo.HttpExtensions.Shared/HttpRequestMessageConfiguration.cs

@@ -36,6 +36,6 @@ public class HttpRequestMessageConfiguration : IHttpRequestConfiguration
 		/// <summary>
 		/// A set of properties for the HTTP request.
 		/// </summary>
-		public IDictionary<string, object> Properties { get; }= new Dictionary<string, object>();
+		public IDictionary<string, object> Properties { get; set; }= new Dictionary<string, object>();
 	}
 }