Dirclean: delete oldest files until dir size is less than threshold

[ncw (Nick Craig-Wood)]

@ErAzOr

What doensn't work is editing existing files (on gdrive). For example if I try to edit TXT files by nano and try to save, I get something like 'illegal seek".

rclone can't open files for read and write together, and it can't seek in write only files. To fix that, rclone would have to buffer files locally which it may one day.