Albatross braille driver: small improvements (#14844)
Summary of the issue:
Added some gestures. Do not try to open port if it is not present.
Description of user facing changes
Added following gestures:
| Shows braille settings | f1+home1, f9+home2 |
| Reads status bar and moves navigator object into it | f1+end1, f9+end2 |
| Cycle the braille cursor shape | f1+eCursor1, f9+eCursor2 |
| Toggle the braille cursor | f1+cursor1, f9+cursor2 |
If there is working connection, and I/O error occurs, port presence is checked before trying to open it again. USB serial port disappears when cable is plugged out or device is powered off, thus efforts to open port are then useless. Debug level log entries are also more readable telling that port is not present instead of exception info.
Description of development approach
Added boolean function _portPresent to class ReadThread in _threading.py.
