relocate serialization code from SQLiteRegionData to MoapModule using load and save events.

This is better modularity.  It also allows MoapModule to be replaced with some other media module that may behave completely differently in the future.
Remaining non-modularity:
PrimitiveBaseShape needs explicit Media and MediaRaw fields.  MediaRaw is required in order to shuttle the pre-serialization data back and forth from the database layer.
The database also needs to know about MediaRaw though not about Media.
IMO, it would be extremely nice to remove these hard codings but this is a bridge too far at the present time.

OpenSim/Framework/PrimitiveBaseShape.cs

@@ -173,6 +173,12 @@ namespace OpenSim.Framework
             }
         }
         
+        /// <summary>
+        /// Raw media data suitable for serialization operations.  This should only ever be used by an IMoapModule.
+        /// </summary>
+        [XmlIgnore]
+        public string MediaRaw { get; set; }
+            
         /// <summary>
         /// Entries to store media textures on each face
         /// </summary>