Just some setter methods

Makes it a lot easier to dummy Etsy responses when you have access to the code & results. See https://github.com/seanoshea/krissytosi-android/blob/81ee89ea586823925bd6962a208161f04f872ccf/krissytositest/src/com/krissytosi/utils/FileSystemStoreApiClient.java for a very simple example of dummying a Listing without having to hit the network.