CSV session Import with hours precision

[NicoDucou]

For the moment when importing session by CSV on main/session/session_import.php DateStart and DateEnd are with format "yyyy/mm/dd" and should be transformed to "yyyy/mm/dd" hh:mm:ss" and make sure this time is correcty taken into account in the importation.

Ref : BT#17767 and BT#17843

[christianbeeznest]

It is implemented in this PR #6220

Thanks for confirmation.