Add tabindex=0 to first panel of collapse if no other panels have "in" class
Add tabindex=0 to first panel of collapse if no other panels have "in" class

This change uses the new hasopenpanel var to check if the current collapse
parent has any children panels that are open (i.e. have "in" class). If not,
it sets the tabindex=0 for the first child panel by default.

paypal/bootstrap-accessibility-plugin,paypal/bootstrap-accessibility-plugin,paypal/bootstrap-accessibility-plugin,paypal/bootstrap-accessibility-plugin,paypal/bootstrap-accessibility-plugin