Squeeze messages to a minimal
number of rows (with no overlap). This allows the user to see as many messages
as possible in a single screen with no need for scrolling of the vertical
axis.
Note: In this case received channel and ID are not relevant,
so the same row may contain messages received from different
stations/coordinators and on different channels4.
4 - HOW IS THIS DONE: messages are sorted according to start time, each message is placed in the first row possible with no time overlap with previous messages.