The fiscal years are created centered on the passed date such that if the
current day change during the execution, the fiscal year is still usable.
Also fiscal year can be created for a range of dates such that it is guarantee
that the dates are in the fiscal year.
And finally remove datetime and dateutil import when they are not used.
Closes#9977
get_required_version does not need to use .dev0 suffix anymore.
The download URL must be empty for development version.
Source Code must point to Heptapod repository.
Foundation email is used as author email.
Maxime Richez