Storage about jzarr

[joshmoore]

Hi @SabineEmbacher, just a few thoughts on this list:

• NestedDirectoryStore and DirectoryStore are basically deprecated by FSStore which I think should be equivalent for FileSystemStore.
• @DennisHeimbigner rightly brought up (somewhere!) that the ZipStore specs really needs to be written down somewhere. If you have issues implementing it for v2, we might want to go through the process of adding a description to v2.rst; but that should definitely be captured in the spec for v3.

[SabineEmbacher]

• DimensionSeparator implemented in ZarrArray
• Allowed separators are "." or "/".
• If an existing array is opened (old style), whose header (".zarray") does not yet contain a "dimension-separator", it is scanned whether there are already written chunks. If so, their dimension_separator is used.