Migrate Keypad PCF8574 from nf-Community-Contribution to Iot.Device

[Ellerbach]

Need some adjustments to fit the IoT.Device requirements. Most likely needs to adjustments as well to fit with the existing keypad in IoT.Devices. Binding to migrate: https://github.com/nanoframework/nf-Community-Contributions/tree/master/drivers/Keypad-PCF8574