#784 Perform bypass purge permission check with OfflinePlayer objects

- Move permission check inside PurgeTask to perform it with OfflinePlayer objects instead of lowercase names
- Move purge members into child "purge" package
- Unify online and offline default permission behavior in DefaultPermission

src/test/java/fr/xephi/authme/AuthMeInitializationTest.java

@@ -12,7 +12,7 @@ import fr.xephi.authme.process.Management;
 import fr.xephi.authme.process.login.ProcessSyncPlayerLogin;
 import fr.xephi.authme.security.PasswordSecurity;
 import fr.xephi.authme.settings.NewSetting;
-import fr.xephi.authme.task.PurgeService;
+import fr.xephi.authme.task.purge.PurgeService;
 import org.bukkit.Bukkit;
 import org.bukkit.Server;
 import org.bukkit.plugin.PluginDescriptionFile;
@@ -93,7 +93,7 @@ public class AuthMeInitializationTest {
         // given
         NewSetting settings = new NewSetting(settingsFile, dataFolder, getAllPropertyFields(), alwaysFulfilled());
 
-        // TODO ljacqu 20160619: At some point setting the "plugin" field should not longer be necessary
+        // TODO ljacqu 20160619: At some point setting the "plugin" field should no longer be necessary
         // We only require it right now because of usages of AuthMe#getInstance()
         ReflectionTestUtils.setField(AuthMe.class, null, "plugin", authMe);