Fixes/improvements to BrailleDisplayProber:
* Add code doc.
* Allow the callbacks to be passed to the constructor.
* Fixed filtering for active/non-active probing. Also, active probing still tries the automatic port, as some ports aren't listed as manual ports for some displays.
* Rename endProbingCallback to noDisplayCallback and call it where appropriate.
* cosmetic: In the generator, return instead of raising StopIteration, as a generator will raise StopIteration itself once there is nothing more to yield.
* Skip a driver if its check method returns False.
* Catch all exceptions from drivers, as not all drivers use RuntimeError.
* Don't continue scanning once a display is found.
