This commit included quite a lot of changes:
* The application arguments are now divided in a read and a write part.
This is realized through structopt subcommands.
* The read and write commands are recognized in a match construction
which takes place after the device is opened.
* I refactored some of the error messages and added more error messages
* The pedals_read() function now is able to read 1, 2, or 3 pedals.
Furthermore, the table is now redrawn with box drawing symbols.
* The write function is tested and successfully writes a key to the
device