#674 PurgeService: Always register if purging, reduce code duplication

- Rename autoPurging to isPurging: we should always register if a purge task is in progress (regardless if autopurge or not) and deny any new requests
- Reduce the same logic being coded multiple times by calling through the methods
- DataSource: remove purgeBanned in favor of purgeRecords, both do exactly the same thing

src/main/java/fr/xephi/authme/command/executable/authme/PurgeBannedPlayersCommand.java

@@ -32,6 +32,6 @@ public class PurgeBannedPlayersCommand implements ExecutableCommand {
             namedBanned.add(offlinePlayer.getName().toLowerCase());
         }
 
-        purgeService.purgeBanned(sender, namedBanned, bannedPlayers);
+        purgeService.purgePlayers(sender, namedBanned, bannedPlayers.toArray(new OfflinePlayer[bannedPlayers.size()]));
     }
 }