Clean up Rev2-Pins and supporting setting multiple pins at once

Hello!

- Changed the GPIOPins-enum in a more clean way. It's now like in the bcm2835.h: every revision has it's own set of pins.

- added the P5-Header GPIOs, they are new in Rev2

- Added the possibility to set/clear multiple pins at once.

Example how to set two  pins at once:

			var D12 = new GPIOMem(GPIOPins.GPIO_01);
			var D15 = new GPIOMem(GPIOPins.GPIO_08);
			GPIOMem.SetMulti(D12.Mask | D15.Mask);

Todo this, you need the latest version 1.16 of the bcm2835 driver.

Greetings,
Sebastian