segmentation -> image mapping

[tgbugs]

See whether there are duplicate filenames the will stimy the naive solution.

[tgbugs]

Do the relative paths go in the manifest or are the original segmentation files updated? If someone wanted to open the files in the tissue mapper at a later date, it would be great to have the relative path in the segmentation file.

[tgbugs]

Note from meeting earlier today is that if we get the remote id for the relative path even a single time we can use that information to update the relative paths in the manifests if the curation team needs to reorganize the hierarchy.