MCU Pins for debugging, LED, boot tracing, and shift registers are now configurable at keyboard level.
Macros led_* replaced by DBG_LED_*
Macros m15_* replaced by DBG_1_*
Macros m27_* replaced by DBG_2_*
Macros m28_* replaced by DBG_3_*
For CTRL and ALT keyboards, debug boot tracing pin default now set to pad M27 instead of M28 since although M28 is not being used, it is technically a signal for USB port detection.
m15_print(...) renamed to dbg_print(...) to get away from hard coded port names.
dbg_print function now follows similar pattern to debug led output.
