Mantis #7567: added an 8-sec expiring item cache to the inventory network connector. This fixed the problem on my local test grid and generally made things faster. This cache has been needed for a while... there are many parts in the code where the sim gets an item multiple times in a short amount of time (rezzing attachs and objects, for example).

Other minor changes:
- added the scene as a parameter to the constructor od FetchInvDescHandler, so that I could see in which scene the handler was being called
- brought linked items in linked folders back to being prefetched

OpenSim/Capabilities/Handlers/FetchInventory/FetchInvDescServerConnector.cs

@@ -67,7 +67,7 @@ namespace OpenSim.Capabilities.Handlers
             m_LibraryService =
                     ServerUtils.LoadPlugin<ILibraryService>(libService, args);
 
-            FetchInvDescHandler webFetchHandler = new FetchInvDescHandler(m_InventoryService, m_LibraryService);
+            FetchInvDescHandler webFetchHandler = new FetchInvDescHandler(m_InventoryService, m_LibraryService, null);
             IRequestHandler reqHandler
                 = new RestStreamHandler(
                     "POST",