Add ability to import files containing events from multiple calendars into separate calendars

[Gitoffthelawn]

Apps like Business Calendar and Business Calendar 2 allow exporting multiple calendars to a single .ics (ical) file. Actually, due to a misleading UI, they encourage it!

If ical-import-export could process such files and import the data into multiple calendars, that would be an incredible feature.

Those popular apps seem to primarily use ORGANIZER:CN=[calendar name] to differentiate which event goes with which calendar.