Update to libWiringPi v2

- Update libWiringPi to v2 (deps folder)
- Move values check into c++ functions
- Update documentation
- exports.js dynamically exports functions from c++ module
- Add support for Physical numbering scheme in setup function
- Reorganise and add some libWiringPi constants
- Added functions: wiringPiSetupPhys, pinModeAlt, analogRead,
analogWrite, wpiPinToGpio, physPinToGpio, setPadDrive, getAlt,
digitalWriteByte, pwmSetMode, gpioClockSet, mcp23s17Setup, ...
- Update package.json (version, contributors)
- Add a lot of comments in source code
- Update examples
- Add all libWiringPi extensions header
- Add support for drcSerial
- Add support for max5322
- Add support for mcp23s17
- Add support for mcp23s08
- Add support for mcp3002
- Add support for mcp3004
- Add support for mcp3422
- Add support for mcp4802
- Add support for mcp23008
- Add support for mcp23016
- Add support for mcp23017
- Add support for pcf8574
- Add support for pcf8591
- Add support for softPWM
- Add support for softServo
- Add support for softTone
- Add support for sr595
- Add support for wiringPiSPI
- Add support for wiringPiSerial (wiringPiSerialPrintf not implemented yet)
- Add support for wiringPiShift