Pluggable Classes

Hello & thanks for the effort!

I think it’d be a good idea to have the classes pluggable by wrapping them into a if(!class_exists(‘…’)) conditional. At the current state, it’s impossible for me as a developer to override any functionality. Also I’d like to have the ability to change the widget output template. For my situation, I need to have all checkboxes outside the label element, which is not achievable in a good manner for me.