added option to clear buffer on resuming the buffer. Enables multiple…

[DiuLaMaX]

… calls to write bags in a succession for different groupings in rosbag files

[davidt315]

By default, the behavior of the package will remain the same where the topic that is being written from the buffer to a rosbag is cleared after writing. However, we found a use case where we could programmatically trigger snapshots for different cases e.g. navigation fails and we record a snapshot, or similarly the gps fails. In the case that multiple programmatic triggers call for snapshots and there is topic overlap, one rosbag would have all the data and since the buffer was cleared, the next rosbag snapshot for the next event shortly after would have no messages in the buffer.

We implemented a simple flag that can be configured with a launch file and uses the same user interaction to add the option to clear the buffer. Since the default is true - clear the buffer, others using the package would see no change and would continue to use the package without change.

[jahaniam]

This is a very useful feature. Can we have this merged, please?