Add support to property mapper for left-over properties without mapping rules

src/property-mapper.js

@@ -62,6 +62,13 @@ module.exports = function createPropertyMapper(propertyMap) {
 				return Object.assign({
 					value: propertyValue
 				}, mappings[propertyName]);
+			} else {
+				return {
+					sourceProperty: propertyName,
+					destinationObject: "_",
+					destinationProperty: propertyName,
+					value: propertyValue
+				}
 			}
 		}).filter((item) => {
 			return (item != null);