Have a way to overwrite import times when importing a file that already exists

[uwidev]

When importing a file that already exists in the database, whether be url or hash, there should be an option to overwrite the existing import time. This is useful for cases where in the past, individual files c, a, b were imported in that order, but then a proper source was found with the right ordering. The importer could then set their import times so they are a, b, c .

Perhaps this could be an import option, allowing it to be ran on a per-job basis.

There's some other cases where a user might want to keep the original import time, but I don't know a use case for that.

My use case for this is to trivially group variations of images together to quickly set them as alternatives. I sort by import time to be able to do this, though by modification time might work as well.

A workaround was found thanks to Zweibach on the Discord as follows. When running an import, files are already sorted by import time. In this case, it's trivially possible to set their import times with manage>times and use cascading steps for all files. Because this exists, this function might not be a big priority.