Partially implement share with group option for object inventory items

If serverside permissions are off then this works as expected.  Previously, it was impossible for more than one person to edit such items even if permissions were off.
If serverside permissions are on then this works as expected if the object was created by an avatar who had the required group active.
However, if the group for the object is later set then the contained item is still not editable.  This may be linked to a wider bug where the object is still not modifiable by the group anyway

OpenSim/Region/Framework/Scenes/Scene.Inventory.cs

@@ -1160,6 +1160,7 @@ namespace OpenSim.Region.Framework.Scenes
                             item = LibraryService.LibraryRootFolder.FindItem(itemID);
                         }
 
+                        // If we've found the item in the user's inventory or in the library
                         if (item != null)
                         {
                             part.ParentGroup.AddInventoryItem(remoteClient, primLocalID, item, copyID);