taxonomy: add anonymize_pcap

Rewrites a pcap file to obscure MAC addresses and SSIDs.

We gather pcaps for the taxonomy unit test, checking them into
taxonomy/testdata/pcaps. Some of the pcaps are from people's
personal devices or from their Wifi networks at home. As we
publish this code and these pcaps, this utility obscures the
MAC address and SSID of people's personal devices before
checking them in.

Change-Id: I743af0231c3e81aec4aa360e69b9e83fecd2475c
10 files changed