When the user stops a script, have it remain stopped

Previously the script state was never saved for a !Running script, so upon region restart the script would be Running again.

The use of the 'StayStopped' flag is needed because all scripts are automatically stopped when the region shuts down, but in that case we shouldn't save in their state that they're !Running.

OpenSim/Region/ScriptEngine/Interfaces/IScriptInstance.cs

@@ -92,6 +92,11 @@ namespace OpenSim.Region.ScriptEngine.Interfaces
         /// </summary>
         bool ShuttingDown { get; set; }
 
+        /// <summary>
+        /// When stopping the script: should it remain stopped permanently (i.e., save !Running in its state)?
+        /// </summary>
+        bool StayStopped { get; set; }
+
         /// <summary>
         /// Script state
         /// </summary>