Add option to show only connection map and suppress frame output

[kpvdr]

It can be a nuisance to scroll up through pages of frame output to see the connection map which is printed at the top, especially with long traces. This option would suppress the packet output altogether and print the connection map only. This makes it easier to select connections to use for the connection filter.

[kpvdr]

There is a workaround: Using the -C/--connection option with a value of 0 will suppress all frame output.