New layout of the calendar for the time fields #45

@gregrickaby please check if it is nice, I applied to all wordpress admin themes
I Removed parameter to remove selects the month and year of the calendar header. 

Over the correct location would be here https://github.com/WebDevStudios/CMB2/blob/master/includes/CMB2_hookup.php#L153-154 

I will correct and send the PR again.