Mantis#1591. Thank you graciously, Sempuki for a patch that:

Currently module loading is done ad-hoc. I propose creating a simple 
loader class that leverages Mono.Addins (and perhaps the new .NET 
addins when they become available in mono). Attached is a basic 
patch for review that compiles into HEAD, but doesn't yet replace 
any existing ad-hoc loaders.

OpenSim/Data/MSSQL/MSSQLAssetData.cs

@@ -218,6 +218,8 @@ namespace OpenSim.Data.MSSQL
 
         #region IPlugin Members
 
+        override public void Dispose() { }
+
         /// <summary>
         /// <para>Initialises asset interface</para>
         /// <para>