Committing the Avination Scene Presence and related texture code

- Parts of region crossing code
- New bakes handling code
- Bakes now sent from sim to sim without central storage
- Appearance handling changes
- Some changes to sitting
- A number of unrelated fixes and improvements

OpenSim/Framework/ILandObject.cs

@@ -70,6 +70,7 @@ namespace OpenSim.Framework
         void UpdateLandProperties(LandUpdateArgs args, IClientAPI remote_client);
         bool IsEitherBannedOrRestricted(UUID avatar);
         bool IsBannedFromLand(UUID avatar);
+        bool CanBeOnThisLand(UUID avatar, float posHeight);
         bool IsRestrictedFromLand(UUID avatar);
         bool IsInLandAccessList(UUID avatar);
         void SendLandUpdateToClient(IClientAPI remote_client);