MaestroAPI: change AddLayer methode of MapDefinition

[gBecker]

Jackie, due to ticket #1941 you changed the AddLayer methode of the MapDefinition class. I think that in most classes of the .NET Framework adding an object to a collection means to append this object at the end of the collection. For new users of the MaestroAPI this could cause some trouble

So, wouldn't it be a better approach to make another InsertLayer methode for the case of #1941:

public IMapLayer InsertLayer(int idx, string groupName, string layerName, string resourceId)

[jng]

Fixed r7171