Implement re-process with a button, rather than a checkbox

[dalonsoa]

• I'm a bit confused by the "Reprocess data" checkbox. I guess it's so you can re-trigger the import if something fails, but wouldn't this be better as a button?

This was implemented when we only had the Admin interface to play with, so the re-process checkbox was the best (only) choice. Now that we have our own custom views, I agree that a button will work much better. I'll open another issue about it.

Originally posted by @dalonsoa in #364 (comment)