time datetype #282

create new \DateInterval by force can be unwanted.
In case the key is primary - script ends with an exception, because \DateInterval doesn't have an __toString() method.

From my perspective would be better to store as string and add a new helper function for creating \DateInterval from string in Nette/utils.

Or much complicated way can be create new Class Nette\Utils\DateInterval exteded of \DateInterval which contain __toString() method - but there is a lots of options formating

Thanks for advice