Merge branch 'zero' of https://github.com/aethaniel/ArduinoZero into usb_valid_host

cores/arduino/Uart.cpp

cores/arduino/Uart.h

cores/arduino/WVariant.h

cores/arduino/startup.c

cores/arduino/wiring_analog.c

cores/validation/validation_I2C_I01/test.cpp

cores/validation/validation_I2C_LCD/test.cpp

cores/validation/validation_I2C_RTC/test.cpp

cores/validation/validation_I2C_multi/test.cpp

cores/validation/validation_PWM/build_as6/test.atsln

cores/validation/validation_PWM/build_as6/test.cppproj

cores/validation/validation_PWM/test.cpp

cores/validation/validation_chuck/test.cpp

cores/validation/validation_core/test.cpp

cores/validation/validation_new/build_as6/test.atsln

cores/validation/validation_new/build_as6/test.cppproj

cores/validation/validation_new/test.cpp

cores/validation/validation_shield_wifi/test.cpp

variants/arduino_zero/variant.cpp

variants/arduino_zero/variant.h