v2.2.0 - Release

Highlights:
-Changes to better support AGT

Changelog:
-add a default Wire for artemis module
-fix low rx causing hangs
-update arduino api to v1.2
-revert i2c change that was causing transfer errors at 100khz
-add SPI_HAS_TRANSACTION define
-add second WIRE for the Explorable
-add platform.json for platformio
-(remove additional targets from attached mbed core)