Changes in the API:
- No more mandatory callbacks declared for each node anymore
heartbeatError
SDOtimeoutError
initialisation
preOperational
operational
stopped
post_sync
post_TPDO
canSend

- Fill function ptr to declare callbacks
CO_Data.heartbeatError
CO_Data.SDOtimeoutError
CO_Data.initialisation
CO_Data.preOperational
CO_Data.operational
CO_Data.stopped
CO_Data.post_sync
CO_Data.post_TPDO

- CanClose now takes CO_Data* as parameter
- canSend is provided to the stack directly by OS interface, no specific callback.

Bug on CanOpen help popup corrected