Added code for selective nozzle cleaning

Use "M100 T1" to clean extruder 1 and "M100 T2" to clean extruder 2 on 2.0/2.0A printers, "M100" or anything other than "M100 T1" or "M100 T2" will clean both.

src/ArduinoDUE/Repetier/Printer.h

@@ -973,7 +973,7 @@ public:
     static void homeAxis(bool xaxis,bool yaxis,bool zaxis); /// Home axis
 //Davinci Specific, clean nozzle feature
 #if ENABLE_CLEAN_NOZZLE 
-    static void cleanNozzle(bool restoreposition=true);
+    static void cleanNozzle(bool restoreposition=true, int8_t extT=-1);
 #endif
     static void setOrigin(float xOff,float yOff,float zOff);
     static bool isPositionAllowed(float x,float y,float z);