Added some place holder classes for various modules.

Some work on the asset cache, can people please test this. including on one of the public systems so we can see if it causes problems with multiple users.

OpenSim/Region/Environment/Modules/TextureDownloadModule.cs

@@ -0,0 +1,49 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+using libsecondlife;
+using OpenSim.Framework.Interfaces;
+using OpenSim.Region.Environment.Scenes;
+using OpenSim.Region.Environment.Interfaces;
+
+namespace OpenSim.Region.Environment.Modules
+{
+    public class TextureDownloadModule :IRegionModule
+    {
+        private Scene m_scene;
+
+        public TextureDownloadModule()
+        {
+
+        }
+
+        public void Initialise(Scene scene)
+        {
+            m_scene = scene;
+            m_scene.EventManager.OnNewClient += NewClient;
+        }
+
+        public void PostInitialise()
+        {
+
+        }
+
+        public void CloseDown()
+        {
+        }
+
+        public string GetName()
+        {
+            return "TextureDownloadModule";
+        }
+
+        public void NewClient(IClientAPI client)
+        {
+        }
+
+        public void TextureAssetCallback(LLUUID texture, byte[] data)
+        {
+
+        }
+    }
+}