Low level period transmits and more

API changes:

• EMCY resets are not handled differently than regular EMCY codes in callbacks and log anymore. Previously None was used to represent a reset in the callbacks and it was not added to the log. Now resets are represented as a EmcyError with code 0.

Improvements:

• Low level periodic transmission is used if the CAN interface and python-can supports it (currently supported with SocketCAN and IXXAT).
• Bit mapping support for PDOs
• EDS files with default value expressions containing $NODEID is supported
• LSS improvements
• If the CAN receive thread crashes, the exception will be raised next time a message is transmitted.