* support for task activation on a status request with arbitrary interval and number of iterations (0 and 1 are still default values)
* implement waitForDelayed() method to allow task activation on the status request completion delayed for one current interval
* added callback methods prototypes to all examples for Arduino IDE 1.6.6 compatibility
* added several constants to be used as task parameters for readability (e.g, TASK_FOREVER, TASK_SECOND, etc.)
* significant optimization of the scheduler's execute loop, including millis() rollover fix option