Import one file into several accounts

Many banks export all accounts in one file (for example a NatWest OFX with your current account and credit card). Today Budgero only sends a row to an account whose name matches exactly, so everything else lands in one account.

Planned:

• When a file contains more than one account, the import dialog lists each one (with how many transactions it has) and lets you send it to an existing account, create a new account for it, or skip it.
• Your choices are remembered per bank account, so next month's download splits by itself.
• Works for OFX/QFX, CAMT.053, CSV/TSV (and the import template) with an Account column, PDF tables, and multi-account QIF exports (Quicken, YNAB4, GnuCash).

Files with a single account keep working as they do now.