[Opensim-dev] Asset services and CommsManager

[Melanie]

With r9598, AssetCache was removed from CommsManager and replaced by 
a new interface, Scene.AssetService.

This is certain to break any applications using asset services, e.g. 
private region modules and Scene subclasses.

The course of removal was taken because the members had no more 
functionality and leaving them in would have allowed the building of 
derived classes and modules that would assume they still function, 
making those fail in nonobvious ways.

By removing this property, anything that would not work any longer 
will break on build or load, letting you know that changes are required.

Melanie