Arduboy2 v5.1.0
Added a flag in system EEPROM to control whether the RGB LED is flashed during the boot logo sequence or left off.
Added library functions writeShowBootLogoLEDsFlag() and readShowBootLogoLEDsFlag() for writing and reading the new flag.
Example sketch SetSystemEEPROM modified to allow setting the new flag.
Added code to mainNoUSB() to make sure the TX and RX LEDs are turned off.