Fix bugs in purge classes, cleanup

- OfflinePlayer objects were never mapped to names
- Essentials purge was run even if setting was disabled
- Console user saw messages twice
- Misc: trivial field reorderings, change DefaultPermission to be null safe
- Permissions: do not expose PermissionHandler just to get its type

src/main/java/fr/xephi/authme/permission/PermissionsManager.java

@@ -217,12 +217,12 @@ public class PermissionsManager {
     }
 
     /**
-     * Get the current permissions system handler.
+     * Return the permissions system that is hooked into.
      *
-     * @return The permissions system handler.
+     * @return The permissions system, or null.
      */
-    public PermissionHandler getHandler() {
-        return handler;
+    public PermissionsSystemType getPermissionSystem() {
+        return isEnabled() ? handler.getPermissionSystem() : null;
     }
 
     /**