- Rename WRITE_E_STEP for consistency

- Add BIT and TEST macros
- Add _APPLY_ macros to stepper.cpp to help with consolidation
- Consolidate code in stepper.cpp using macros
- Apply standards in stepper.cpp
- Use >= 0 instead of > -1 as a better semantic
- Replace DUAL_Y_CARRIAGE with Y_DUAL_STEPPER_DRIVERS

Marlin/pins.h

@@ -184,4 +184,6 @@
                         analogInputToDigitalPin(TEMP_BED_PIN) \
                        }
 
+#define HAS_DIGIPOTSS (DIGIPOTSS_PIN >= 0)
+
 #endif //__PINS_H