Change event handlers arguments signature

[gpbl]

The current event handlers such as onDayClick have a signature which puts the Synthetic Event as first argument:

onDayClick={ (e, day, modifiers) => doSomething(day); }

however it is expected the most common arguments to be day and modifiers:

onDayClick={ (day, modifiers, e) => doSomething(day); }

which can lead to a more concise, readable code:

onDayClick={ doSomething }