Request: Save goodparticles.star as a file series

[hnndlp]

If instead of the last10000 file, files were saved as blocks of say 400K particles (or a user specified amount), it would make it possible to process on the fly in Relion and simply join star files at the end. This would be very useful for 2D classes. One could jump right into 3D shortly after the last movie is collected.