Added initial Melody Playback Ability

Now, controlled via MQTT a Playback of a melody can Start, Stop, Pause 
etc. 

Settings like speed, total duration, pauses etc can be set.

bellEngine.hpp

@@ -0,0 +1,68 @@
+// MELODY PLAYBACK WILL BE HANDLED HERE
+#include <vector>
+
+extern melody_attributes melody;
+extern uint16_t relayMask;
+
+void loop_playback(std::vector<uint16_t> &melody_steps);
+void itsHammerTime(uint16_t note);
+
+
+void bellEngine(void *parameter) {
+
+	// SETUP TASK
+
+	for (;;) {
+
+		// Playback until stopped (Completes AT LEAST 1 full loop)
+		loop_playback(melody_steps);
+
+ /*
+		UBaseType_t highWaterMark = uxTaskGetStackHighWaterMark(NULL);
+		Serial.print("Stack high water mark: ");
+		Serial.println(highWaterMark);
+ */
+	}
+
+}
+
+
+void loop_playback(std::vector<uint16_t> &melody_steps) {
+
+	while(melody.isPlaying && !melody.isPaused){
+
+		// iterate through the beats and call the bell mechanism on each beat
+		for (uint16_t note : melody_steps) {
+			if (melody.hardStop) return;
+			itsHammerTime(note);
+			int tempo = melody.speed;
+			vTaskDelay(pdMS_TO_TICKS(tempo));
+		}
+
+		Serial.println("SINGLE LOOP OVER.");
+    //if (!melody.isPlaying) break;                  // Stop playback only after completing the loop
+
+	}
+
+}
+
+
+void itsHammerTime(uint16_t note){
+
+	// THIS NEEDS REWORK, TO WAIT, DYNAMICLY PER RELAY
+	// MUST BE CONFIGURABLE REMOTELY
+
+	for (uint8_t i=0; i<16; i++) {
+			if (note & (1 << i)) {
+				relays.digitalWrite(i, LOW);
+			}
+		}
+
+	vTaskDelay(pdMS_TO_TICKS(relayDurations[0]));
+
+	for (uint8_t i=0; i<16; i++) {
+		relays.digitalWrite(i, HIGH);
+	}
+
+
+}