Add xf table prefix to config

#957

src/test/java/fr/xephi/authme/settings/properties/AuthMeSettingsRetrieverTest.java

@@ -22,7 +22,7 @@ public class AuthMeSettingsRetrieverTest {
         // an error margin of 10: this prevents us from having to adjust the test every time the config is changed.
         // If this test fails, replace the first argument in closeTo() with the new number of properties
         assertThat((double) configurationData.getProperties().size(),
-            closeTo(160, 10));
+            closeTo(171, 10));
     }
 
     @Test