4.8.1-jre8

Release 4.8.1 JRE 8

• Make specific Checkout exceptions extend CheckoutException
• Removed deprecated Events and CountryCode string references
• Added @Builder.Default to PaymentRequest metadata (FOUR)
• Added name and city attributes to BillingDescriptor (FOUR)
• Removed redundant enum lookup methods
• Minor fixes on CVV card payment mappings