raster 3.0
#2002 Relevant changes in this commit: Added LayerOrderManager interface; Added "orderManager" field in MapContext class (so it is persisted); FLayers objects will use the order manager of their MapContext; Added methods to MapContextLocator to register order managers; Added two implementations in "mapcontext.impl"; Added layer order preferences page; Current order manager is persisted in main plugin persistence; Layer order manager is set when a new view is created and cannot be changed, so you can have views with different order managers.