Instant payment feature

Introducing a new feature called "Instant Payment".

Technically "instant payment" is an authorisation with an additional parameter sent along - "captureDelayHours" = 0. It means that funds will be captured immediately right after a successful authorisation.

By default Adyen captures funds 2 days after the successful authorisation (this option can be changed, though) and this is a general setting for all the payments. 

"Instant payment", on the other hand, overrides that setting and allows you to adjust it per payment.

P.S Can be refactored to an integer value - duration in hours after the authorisation prior to capturing funds.