Generate poll options automatically for each day in a period

[lucaa]

Very often polls are used to check people availability for a date: a meeting date or any other event date.

In these cases, the options of the poll are, most of the times, calendar dates (but could be mixed with something else).
This issue is about adding a new feature to the poll creation form / wizard to allow the creator to add easily all the dates in a period to the poll. The user would select a start date for the period and an end date for the period and options would be generated automatically for each date in the period. The options should remain editable after automatic generation, so that some dates could be excluded afterwards.

This feature would be only a helper to avoid the polls creators typing, no other poll options constraint should be added as part of this feature.