Allow one to move pcap files between nodes

[rful011]

As per conversation on the Google group: At the moment the session record has reference the pcap file by number and node. This means that one can not easily move the pcap files around to balance storage.

there are a couple of ways that I can think of to make this possible:
1/ each entry in the file index has a unique ID and this is what is referenced by the session 2/ add the ability to chain entries in the file index