Update the logic for ProxyAndRecord (#747)

* .

* set

* .

* .

* .

* .

* prio

* appsettings

* TinyMapperUtils

* set

* p

* nullable

* .

* ,

* fs

* .

* .

* --PreferProxyMapping

src/WireMock.Net.Abstractions/Admin/Mappings/MappingModel.cs

@@ -25,7 +25,7 @@ namespace WireMock.Admin.Mappings
         public string Title { get; set; }
 
         /// <summary>
-        /// The priority.
+        /// The priority. (A low value means higher priority.)
         /// </summary>
         public int? Priority { get; set; }