Add ability to specify start date for recurring events

[sethjeffery]

This adds the option to specify { from: true } so that when picking a recurring rule, it will show the date field with a label of "Start date".

It only changes the view helper, not any validation logic. So date is still considered optional for recurring events.

[rexblack]

Thanks for contributing. Makes sense. Sorry that i didn't comment earlier, I'm so f** busy. I'll have to test it...