Performance enhancements in IODevice::loop() function.
Improved error handling, device is placed off line if not responding.
Improved error reporting, device shown as offline if not operational (faulty or not present).
When writing to analogue outputs pins, the digital _read() function now returns the 'busy' status of the analogue pin. Consequently, the _isBusy() function becomes superfluous and has been removed. The static IODevice::isBusy() function now calls the object's _read() function instead.
Also, limit in DFPlayer of 3 pins has been removed.
