show all options when printing help message

Signed-off-by: Luka Perkov <luka.perkov@sartura.hr>
add flag to stop capture after receiving specified number of packets

Signed-off-by: Luka Perkov <luka.perkov@sartura.hr>
add flag to stop capture after reaching specified size

Signed-off-by: Luka Perkov <luka.perkov@sartura.hr>