Improve formatting of Pay()
Improve comments of Pay()
Initial commit of a Purchase Order payment option
Setting the Transaction.status inside of the payment component.

This used to happen in Transaction::completeUserAndTransactionData(),
but that does not allow the payment components to set their own statuses.
Make the payment type specific view alterations more modular.
Allow controller override
Add the changePaymentInput(), as these will be handled by each element.
New style of displaying the payment options

This will allow us to use multiple payment options at once. i.e PaySimple and Purchase Orders