(icalendar-version): Increase to "0.17".
(icalendar-import-format): Doc fix. Allow function type.
(icalendar--read-element): Doc fix.
(icalendar--parse-summary-and-rest): Doc fix. Handle function
type icalendar-import-format. Make regexps non-greedy.
(icalendar--format-ical-event): Handle function type
icalendar-import-format.
(icalendar-import-format-sample): New function.