Add --no-tiles option to write metadata only

[melissalinkert]

Super quick thought on glencoesoftware/omero-zarr-pixel-buffer#11 (comment), but not thoroughly tested. Mostly just to capture the suggestion from @sbesson so we don't forget.

[sbesson]

Finally managed to to test this PR. The overall output looks good

sbesson@Sebastiens-MacBook-Pro-3 bioformats2raw % ./bioformats2raw-0.10.0-SNAPSHOT/bin/bioformats2raw "test&sizeX=10000&sizeY=20000.fake" test.zarr --no-tiles
sbesson@Sebastiens-MacBook-Pro-3 bioformats2raw % find test.zarr 
test.zarr
test.zarr/.zattrs
test.zarr/.zgroup
test.zarr/0
test.zarr/0/.zattrs
test.zarr/0/.zgroup
test.zarr/0/0
test.zarr/0/0/.zarray
test.zarr/0/7
test.zarr/0/7/.zarray
test.zarr/0/6
test.zarr/0/6/.zarray
test.zarr/0/1
test.zarr/0/1/.zarray
test.zarr/0/4
test.zarr/0/4/.zarray
test.zarr/0/3
test.zarr/0/3/.zarray
test.zarr/0/2
test.zarr/0/2/.zarray
test.zarr/0/5
test.zarr/0/5/.zarray
test.zarr/OME
test.zarr/OME/METADATA.ome.xml
test.zarr/OME/.zattrs
test.zarr/OME/.zgroup
sbesson@Sebastiens-MacBook-Pro-3 bioformats2raw % cat test.zarr/0/0/.zarray 
{
  "chunks" : [ 1, 1, 1, 1024, 1024 ],
  "compressor" : {
    "clevel" : 5,
    "blocksize" : 0,
    "shuffle" : 1,
    "cname" : "lz4",
    "id" : "blosc"
  },
  "dtype" : "|u1",
  "fill_value" : 0,
  "filters" : null,
  "order" : "C",
  "shape" : [ 1, 1, 1, 20000, 10000 ],
  "dimension_separator" : "/",
  "zarr_format" : 2
}%   

And I was able to consume the new API in the context of the original tests and remove the in-place metadata modification without waiting for minutes to generate.

Having the possibility of quickly creating such a spare Zarr datasets feels advantageous I will perform additional testing with different modalities but should this be moved out of draft for a formal review? Minimally, we should at least include some unit tests. In terms of the option name, --no-tiles works for me, alternative names could be --metadata-only or --sparse.

[melissalinkert]

👍 Yes, I can add some tests and then take this out of draft.