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/MySQL/MySQLAssetData.cs

@@ -39,7 +39,7 @@ namespace OpenSim.Data.MySQL
     /// <summary>
     /// A MySQL Interface for the Asset Server
     /// </summary>
-    internal class MySQLAssetData : AssetDataBase, IPlugin
+    internal class MySQLAssetData : AssetDataBase
     {
         private static readonly ILog m_log = LogManager.GetLogger(MethodBase.GetCurrentMethod().DeclaringType);
 
@@ -109,6 +109,8 @@ namespace OpenSim.Data.MySQL
 
         }
 
+        override public void Dispose() { }
+
         #region IAssetProvider Members
 
         /// <summary>