How to export all falling sequences into the same folder about dataset_synthesizer

[thangt]

@bjbraun How did you export all pictures enumerated into one folder, when you were dropping the objects five times in the same location for the FAT dataset? => for FAT, I used GroupActorManager (you can see it in the default map which use this class to spawn distractors) to spawn the training objects with SpawnDuration set to 5 seconds.
When SpawnDuration set to a value > 0, it will spawn new set of object in a volume higher than the surface, wait for objects to fall down and respawn a new set.
The reason I don't have option in the SceneCapturer to add new captured files to an existing directory is we need to maintain the correct settings file: camera and objects, if the user change the camera settings then suddenly the old settings file are incorrect. Although it's doable, that settings will be quite error prone to the user.