Added Effect::start() and Effect::stop() to allow effects to reserve memory on start and free it afterwards.

src/mqtt.cpp

@@ -22,7 +22,9 @@ void mqtt_callback(char* complete_topic, byte* pl, unsigned int length) {
       EffectEntry e = effects->get(i);
       if (strcmp(e.name, payload)==0) {
         //Serial.printf("Effect found in mqtt_callback: %p\n", (void *)&e->effect);
+        current_effect->stop();
         current_effect = e.effect;
+        current_effect->start();
         clear();
         return;
       }