mp3: Remove one level of struct for granales
dump: Makes it a bit easier to understand array of arrays/structs.
avro_ocf: Rename ocf.go -> avro_ocr.go to have same name of source file as format
pcap,pcapng: Rename tcp flow struct to tcp_connection, makes more sense i think
mp4: Add ISOBMFF to format description
Refactor to use groups between network layers to make them less coupled and reusable:
link_frame (ethernet etc)
inet_packet (ipv4,ipv6 etc)
ip_packet (tcp packet (not stream), udp segment etc)
Rename data to payload as i think it makes more sense for network data
