Populate metadata Image dtype

[will-moore]

This allows the Populate_Metadata script UI to pick Image types.

To test:

• Run on https://merge-ci.openmicroscopy.org/web/webclient/?show=image-39715 (csv already attached)

[sbesson]

I am aware that ome/omero-cli-server#5 contains the ongoing discussion about how to express the dependencies for this Python packages on OMERO.server. However, I wonder whether setup.py should not include and install_requires block that would capture these requirements as well (in the case of this PR, I assume omero-metadata>=0.6.0)

[sbesson]

Tested in conjunction with ome/omero-web#264. The script works as expected, taking the input CSV and generating a table alongside the original CSV

Two additional thoughts:

• should the script help be updated to reflect the fact that metadata can be populated for ROIs at the level of the images?
• coming back to the considerations Populate metadata Image dtype #184 (comment), do we need to handle the case where the scripts would be upgraded by not the underlying library?

[will-moore]

We only add Image to the types if from omero_metadata.populate import ParsingContext passes.
However, if I have installed an older version of omero-metadata e.g. v0.5.1 when Image wasn't supported, I get this error if I try to use an Image:

    self.value_resolver = ValueResolver(client, target_object)
  File "/Users/wmoore/Desktop/METADATA/omero-metadata/src/omero_metadata/populate.py", line 338, in __init__
    'Unsupported target object class: %s' % self.target_class)
omero_metadata.populate.MetadataError: Unsupported target object class: <class 'omero.model.ImageI'>

I guess we could detect the support for Image with from omero_metadata.populate import ImageWrapper, but that might not be very reliable. It could be renamed or removed.
I don't know if there's a reliable way to get the version number and show "Please upgrade" if it's not recent or latest?

Otherwise, we should at least state on the omero-metadata README (and omero-guides if they mention this workflow) that Image/ROIs support was added in v0.6.0. Although, a user won't necessarily know what version is installed on their server.

[will-moore]

That last commit tests to see if ImageWrapper is supported in the current version of omero-metadata if the user has chosen an "Image" dtype.
If not, return a suitable message:

[joshmoore]

I like the feedback to the users if it's not installed. (Better would of course be if scripts could have dependencies. One day...)

I could see having the "Please update" message have a red X rather than a green check, but that's not a strong feeling. 👍