Also fixes an issue where sitting avatar counts became inaccurate after any cross.
Part of the problem was due to cloning code using MemberwiseClone() but not resetting certain collection structures.
Adds regression test for this case.
In relation to http://opensimulator.org/mantis/view.php?id=7050
Root cause was that PrimLimitsModule was not properly handling the case where the parcel it was asked to check was outside the current region's bounds.
If this is the case, we can abort the check since the receiving region will perform it.
Added a regression test for this case.
