Adaptation of ListOfOphaalpuntenToContact::UpdateOphaalpunt()

never add more than 1 year

take the maximum of:
	1) the date that is already filled in
	2) the newly calculated date
	3) the current date
Error-handling in KiesOphaalpunten
prefer to use QVariant in item->SetData()
Set Default Locale in main.cpp
Minor changes to UI of InfoOphaalpunt
Start of ListOfOphaalpuntenToContact()