Distinguishing between whether onSelect occurs on a day, month, or year.

[Casey Wilson]

@clauderic thank you so much for creating this awesome library! I love it.

Is there any way to distinguish in the onSelect callback whether the date that was selected was just the year, the month, or the day? I'm working on a project where we want to enable users to select a year or month+year combination without necessarily selecting a whole date.

Also, if the header is hidden by setting showHeader to false, is there any way to create a button to enable the user to go back to the years+month view from the calendar days view?