Changed import workflow

-Rearrange favorites in fs dock with drag and drop
-Removed import -> sub-scene, moved to scenetree contextual menu
-Removed import -> re-import , moved and integrated to FS dock
-Added ability in FS dock to re-import more than one resource
simultaneously
-Added ability to drag from native filesystem explorer to Godot, only
works on Windows though
-Removed scene reimport merge options, never worked well. Eventually
merging materials should be re-added
-Added ability to set custom root node type when importing scenes
-Re-Import is now automatic, can be configured back to manual in editor
settings
-Added resource previews in property list for many resource types

servers/visual/rasterizer.h

@@ -542,6 +542,7 @@ public:
 		RID skeleton;
 		RID material_override;
 		RID sampled_light;
+		Vector<RID> materials;
 		Vector<RID> light_instances;
 		Vector<float> morph_values;
 		BakedLightData *baked_light;