payment_method: add more details from PayPal

During the GetExpressCheckoutDetails call, we stored all the relevant
information regarding the PayPal account. Retrieve them for the
get_payment_method_detail call.

Signed-off-by: Pierre-Alexandre Meyer <pierre@ning.com>
db: add index to paypal_express_responses table

Signed-off-by: Pierre-Alexandre Meyer <pierre@ning.com>
version: update to 1.0.16

Signed-off-by: Pierre-Alexandre Meyer <pierre@ning.com>