Wrote OfferIdentifier and updated ProductRetriever

src/main/java/de/rwu/easydrop/core/OfferIdentifier.java

@@ -20,7 +20,7 @@ public class OfferIdentifier {
     ProductRetriever productRetriever;
 
 
-    public OfferIdentifier() throws ConfigurationException {
+    public OfferIdentifier() {
         Config config = Config.getInstance();
         this.webshops = config.getProperty("WEBSHOPS").split(",");
     }