remove 32 and 16 PPQN callback. keep 96 for compatibility. Added a polling call to avoid jitter(teensy has power to make use of polling)

src/uClock.cpp

@@ -113,6 +113,8 @@ uClockClass::uClockClass()
 	ext_interval_acc = 0;
 	resetCounters();
 
+	onClock96PPQNCallback = NULL;
+	
 	// first interval calculus
 	setTempo(tempo);
 }