Converting between xarray and dataset should preserve image name

[ctrueden]

The name property of DataArray matches up with getName() of Dataset and ImgPlus.

[thewtex]

Hi Curtis! I also ran into this here: spatial-image/multiscale-spatial-image#23

Additional note -- it was helpful to convert getName() from a Java String object to a Python string with str so it could be serialized to Zarr:

# The DataArray name needs to be set
image_da.name = str(image.getName())

[ctrueden]

Thanks @thewtex. I commented on your PR. I also filed #200 here to cover the conversion issue leading to serialization woes.