publish /clock topic for more usability #22
Description
The /clock topic in ROS is usually used for synchronizing with external/simulation time but also required when working with recorded data. Without the topic you can't use the --use-sim-time flag and therefore you would have the problem that a new rosbag-record of a bag file has some invalid timestamps (bag file created with current system time, message with record time).
Since we already have a time_mode flag to define if we want to use the external ADMA INS time or current system time, we could add the /clock topic with an optional flag.