Change references to BLDCDriver to FOCDriver in current sense base class

change setPwm function in FOCDriver to accept 3 args, with a default value for the 3rd

Change stepper driver classes to use 3 arg setPwm, ignoring 3rd arg.

created InlineCurrentSenseSync class in lib/currentsense.

fixed timer bug in calibrate encoder, in main

defined a label for serialusb, to make it easier to swap out.

firmware/lib/Arduino-FOC/src/drivers/StepperDriver2PWM.h

@@ -58,7 +58,7 @@ class StepperDriver2PWM: public StepperDriver
      * @param Ua phase A voltage
      * @param Ub phase B voltage
     */
-    void setPwm(float Ua, float Ub) override;
+    void setPwm(float Ua, float Ub, float NOT_USED=NOT_SET) override;
 
   private: