Run program after importing a pcap

[peace-maker]

Add an option to run arbitrary programs after a new pcap was imported. The program could get the path to the imported .pcap file as an argument. This would be useful for external tools to analyze the pcap and add additional info to the streams, but only after pkappa2 knows about the streams itself.

We could add another pcap_postprocessor directory containing all the programs that should be run after the importPcapJob job.