Add CreatedAt field to quote export report

Include the CreatedAt field in the quote export report. Since the export's date filter operates on the quote's created date, the report should expose that field so filtered results can be verified and audited. Additionally, add "Sent" as an option in the export so that the dollar amount of quotes sent within a given time period can be reported. Clarify which fields the date filter applies to when filtering by statuses such as "Waiting on Approval" or "Approved": whether inclusion in the report is based on the CreatedAt date or on other fields.