Regenerating Nimbus files should obsolete Echo COC files

[cameron-jack]

Regenerating Nimbus files does not cause Echo COC files to become obsolete. They should, even if their contents is the same, just to be safe.

[cameron-jack]

This will be fixed in a major update next week, v0.29.000, which will be a breaking change, billboard tracking all files (uploaded and generated) and creating virtual plate entries for files without plate info. Delete queues will hold all deletion info for plates and files, and the user will be prompted whether to proceed. Experiment.reproducible_steps[filename] will include the virtual plates if needed. Replacing files or plates will result in these being search for and the earliest entry causing all later stages to be added to the delete queues. We will also need an action queue that can proceed with the changes once the deletions complete.