Use "Native Interop" for IO

LibBCM2835 is no longer used and has been replaced with low-level
Interop from Libc
MemoryGpioConnectionDriver Refactoring
HC-SR04 connection improvements
Updated .md
Updated comments and documented samples
Added support for pull-up/pull-down resistor
Enabled package restore
Introducing GpioConnectionDriver, intended for mixed-mode (memory for read/write accesses, file for edge detections)
Introduced IGpioConnectionDriver.Wait and .SetPinDetectedEdges
Removed unused files