Added export_from_date feature

[jeremyharper]

Added an option to skip exporting events older than a given date, useful for making regular exports to a PC (so you don't have to re-export the whole iPhoto database each time).

[BMorearty]

Thanks for the pull request, @jeremyharper.

Is this intended to be different from the existing import_from_date feature?

[jeremyharper]

Yes.

The import feature appears to be designed to take folders from the destination folder and import them back into iPhoto, and the import_from_date feature limits that import process to only folders created after a certain date.

export_from_date limits the export from iPhoto to only events created after a certain date rather than exporting the whole iPhoto library.