Added IO_I2CDFPlayer.h to support DFPLayer over I2C connected to NXP SC16IS750/SC16IS752 (currently only single UART for SC16IS752)
Added enhanced IO_I2CDFPLayer enum commands to EXRAIL2.h
Added PLAYSOUND alias of ANOUT to EXRAILMacros.h
EXRail additions as per advice from Chris
