Make ResendAppearanceUpdates = true by default in [Appearance] in OpenSimDefaults.ini.

This resends appearance uuids to avatars in the scene once a minute.
I have seen this help in the past resolve grey appearance problems where viewers have for unknown reasons sometimes ignored the packet.
The overhead is very small since only the UUIDs are sent - the viewer then requests the texture only if it does not have it cached.
This setting will not help with cloudy avatars which are usually due to the viewer not uploading baked texture data or uploading something that isn't valid JPEG2000

OpenSim/Region/Framework/Scenes/Scene.cs

@@ -861,6 +861,8 @@ namespace OpenSim.Region.Framework.Scenes
             }
 
             // FIXME: Ultimately this should be in a module.
+            SendPeriodicAppearanceUpdates = true;
+            
             IConfig appearanceConfig = m_config.Configs["Appearance"];
             if (appearanceConfig != null)
             {