Implements PayPal Subscription payments

<span style="color: rgba(0, 0, 0, 0.701961); font-family: UICTFontTextStyleBody; line-height: normal; -webkit-composition-fill-color: rgba(130, 98, 83, 0.0980392); text-decoration: -webkit-letterpress;">We would like to implement Recurring Payments/Subscription payments using PayPal on our website. Payments work like this:</span><div style="color: rgba(0, 0, 0, 0.701961); font-family: UICTFontTextStyleBody; line-height: normal; -webkit-composition-fill-color: rgba(130, 98, 83, 0.0980392); text-decoration: -webkit-letterpress;">1 user clicks on a subscription button and gets redirected to the paypal website with the payment option</div><div style="color: rgba(0, 0, 0, 0.701961); font-family: UICTFontTextStyleBody; line-height: normal; -webkit-composition-fill-color: rgba(130, 98, 83, 0.0980392); text-decoration: -webkit-letterpress;">2 once the user has paid we enable the account or provide other access to the user. This will be based on the IPN message</div><div style="color: rgba(0, 0, 0, 0.701961); font-family: UICTFontTextStyleBody; line-height: normal; -webkit-composition-fill-color: rgba(130, 98, 83, 0.0980392); text-decoration: -webkit-letterpress;"><br></div><div style="color: rgba(0, 0, 0, 0.701961); font-family: UICTFontTextStyleBody; line-height: normal; -webkit-composition-fill-color: rgba(130, 98, 83, 0.0980392); text-decoration: -webkit-letterpress;">Language: ruby</div><div style="color: rgba(0, 0, 0, 0.701961); font-family: UICTFontTextStyleBody; line-height: normal; -webkit-composition-fill-color: rgba(130, 98, 83, 0.0980392); text-decoration: -webkit-letterpress;">DB used: mysql</div>