The property will always be set in the future.
We no longer can use it as an indicator.
We switch to freq as new indicator.
We also ensure that start has to be given for a single date.
Relates: #9892
It is now possible to create "Import" records in TYPO3 system.
Those records can then be imported via two new commands.
There is no need to configure everything within the command itself.
That allows:
* To allow editors to maintain import configuration.
* Have proper labels, description, csh and UI to create import.
It no longer is necessary to copy UIDs,
instead proper wizards from TCA are available to select pages.
Relates: #9649
