dir segments

This kind of segment stores all data inside a directory, with one file per datum.

It is suitable for formats that do not support contatenation, like ODIMH5, or for storing data that could be concatenated but is very large, like high-resolution GRIB files.

Files are numbered sequentially, starting from 0. The name of each file is the sequence number, and its extension is the format of the data it contains.

The directory also contains a .sequence file that is used for generating sequence numbers when appending to the segment.

The directory name represents the period of time stored in the segment. The directory extension represents the format of the data it contains.