No default shipping

for osCommerce Online Merchant v2.2

I often received orders with a wrong shipping method selected. By default oscommerce selects the cheapest method (which in my case is 'pickup' since its free). It appears that customers sometimes simply proceed to payment/checkout without realizing that it will not get shipped this way. When the customer receives the order status update saying its order is ready to be picked up, the mistake is first seen and the customer requests to ship it anyway, which causes another update to the order changing the shipping method and the customer must pay the shipping costs in advance. This all costs a lot of work and this contribution aims to PREVENT the customer from making the mistake. This is done as follows: - No shipping method is selected by default (so the customer MUST choose one) - When customer attempts to proceed to payment a JS message is shown (similar behavior to checkout_payment)