Import SAFE rows from a spreadsheet

Reads a spreadsheet kept in the archive (CSV or XLSX) with mapping, each register field's column counting from 0, or a guess from its headers. dry_run, the default, shows each row as it would import: a SAFE with its values and its PDF in the archive when the names match, a row missing something (emails can be given by row), a row imported before, or another security, kept in the archive and not imported. Without dry_run, the complete SAFE rows become Executed SAFEs with Unconfirmed register entries in round_id, or Before Binderwork.