Feature request #8596: Allow empty dates for RemoteControl add_response

This would be helpful for prefilling answers using RemoteControl API instead of passing them in the URL.  I don't think it should cause issues with existing implementations.  For each date, if it is not passed in the date will still be set to the current date.  If a date is passed in it will be set, and if it is passed in with a value of false, null, etc. the date field will not be populated.  

Before this change it's not possible to use add_response without having all of the dates set, even if you pass  a date in as false, null, '', etc.