Documentation enhancements and code cleanups.

Signed-off-by: Tobias Lorenz <tobias.lorenz@etas.com>
Bug fix for sending CAN FD frames will DLC>8.

Signed-off-by: Tobias Lorenz <tobias.lorenz@etas.com>
Cleanup of code.

* Get rid of unused constants / variables / resources / files.
* Improve coding style
* Improve documentation

Signed-off-by: Tobias Lorenz <tobias.lorenz@etas.com>