Offline transactions and option to authorise only

* Added support for recording PinPayments transactions offline.
* Added option to capture and authorise imediatelly, or only postpone capture until invoice creation.
@jonpday Can you please review?
@jonpday The contents of these inputs will only be sent to PinPayments via ajax.  They won't be sent to Magento because the inputs don't have a name attribute. I just double checked by reviewing the HTTP traffic.