First pass at new-and-updated import from archive

- parameters passed to archive methods
- dates saved on entities
- date on covers and book records checked

TODO:
- dialog to select kind of restore to do
- incremental BACKUP
- make sure covers are backed up when doing incremental backup
Incremental import done

- new dialog to ask what kind of import
- checks for old archives (with bad dates)
- progress shows actual update/add counts