#761 Restore permission group in sync with limbo players

- Couple AuthGroupHandler closer to the LimboService: whenever a limbo player is restored, the auth group should be restored as well. This fixes some consistency issues.
- Move AuthGroupHandler into limbo package and make it package-private
- Change permission handler to skip any empty groups (prevents odd command output e.g. for BukkitPermissions)

src/main/java/fr/xephi/authme/process/register/ProcessSyncEmailRegister.java

@@ -3,7 +3,6 @@ package fr.xephi.authme.process.register;
 import fr.xephi.authme.ConsoleLogger;
 import fr.xephi.authme.data.limbo.LimboService;
 import fr.xephi.authme.message.MessageKey;
-import fr.xephi.authme.permission.AuthGroupType;
 import fr.xephi.authme.process.SynchronousProcess;
 import fr.xephi.authme.service.CommonService;
 import fr.xephi.authme.util.PlayerUtils;
@@ -24,9 +23,7 @@ public class ProcessSyncEmailRegister implements SynchronousProcess {
     }
 
     public void processEmailRegister(Player player) {
-        service.setGroup(player, AuthGroupType.REGISTERED_UNAUTHENTICATED);
         service.send(player, MessageKey.ACCOUNT_NOT_ACTIVATED);
-
         limboService.replaceTasksAfterRegistration(player);
 
         player.saveData();