Apply surcharge for paypal entries

Option to add a defined amount (eg 3 percent) onto PayPal entries when offering both PayPal and bank transfer. This means that if they have both options available, that the price must change when switching between PayPal and bank transfer in the enter screen. 

Another reason for doing this is that English congresses have to pay the whole ECF pay to play fee for non members, but the PayPal fees are effectively spread across the whole congress costs, meaning that members are subsidising non members.