[IMP] web: Ask user to confirm export template removal

PURPOSE:

When users try to delete records in the database, we usually warn them about the possible damage they would cause by asking them to confirm this is what they want to do (just in case you misclicked for example)

Unfortunately, that feature wasn't implemented everywhere, at least no in the export window, which means a user can remove ir.exports records without having to confirm that's indeed what he wants to do.
This got worsened by the fact, in the export window (like pictured in the attachment), the "Save field list" button is less than 10px away from the DELETE button, meaning you could really remove 10min of your work (or worse, anybody else's work as we don't have any specific record rule on that) in one click