Add save file to 'finaliseer reis' routine
Added checkbox for 'voyage underway'

Added a checkbox in the VAARPLAN sheet to indicate that the voyage is
under way. When the checkbox is clicked, the color of the ship's name and
IMO number will change (blue for true, and green(ish) for false.
3.4: Locked worksheet 'VAARPLAN'

Locked the 'VAARPLAN' worksheet, to let the user 'tab' trought the input
fields. Added a 'lock' and 'unlock' routine, to let the code fill in
blocked cells. No password is set for the worksheet.
Discarded IMO number as input parameter