ll: Add connection context structure
ll: add ll_pdu_data struct for Data packets
ll: distinguish between CONNECTION_MASTER and CONNECTION_SLAVE states
ll: Go to CONNECTION_MASTER state and setup radio and timer cb
ll: in CONNECTION_MASTER state, implement supervision timeout
ll: in CONNECTION_MASTER state, implement ack/flow control
ll: in CONNECTION_MASTER state, first support of LL Control PDUs
ll: in connection state, limmited support of LL control PDUs
(version exchange only at the moment)
ll: implement connection termination
ll: implement data sending in connection state
ll: add events and callback function for connection state
examples: add ll-connection-master example