Implemented interface for controlling RGB Led
Added RGB Led notifications based conditional compilation using macros
Updated binaries using latest code
Updated to latest binaries
Completed RGB notifications and user control (Tested on Core)
Merge branch 'feature/rgb-control', close #9095713272910

Conflicts:
	build/core-firmware.bin
	build/core-firmware.elf
	build/core-firmware.hex
Implemented Arduino's shiftIn() & shiftOut()
Implemented Spark.deviceID()
Re-request chunk on timeout (refer latest core-communication-lib)
Clean up variable names
TwoWire (I2C) bug fix - Added timeout in blocking methods
Remove warnings-as-errors flag

See: https://community.sparkdevices.com/t/use-of-arduino-stringobject/819/8
Implement Spark.variable introspection functions
Merged with latest master branch