Add some basic summary stats for pcap

[gfr10598]

This introduces basic summary stats for pcap files. It introduces "raw" and "a" records, and fields that will hopefully be easy to reach consensus on.

It also adds a small package for decoding pcap files, as the gopacket package is not very efficient. We also have prototype implementations for decoding ethernet, ip, and tcp headers that will be added later.

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This change is 

[coveralls]

Pull Request Test Coverage Report for Build 7099

• 155 of 277 (55.96%) changed or added relevant lines in 4 files are covered.
• 2 unchanged lines in 1 file lost coverage.
• Overall coverage decreased (-0.6%) to 63.635%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
parser/pcap.go	13	21	61.9%
tcpip/tcpip.go	67	89	75.28%
headers/ip.go	72	164	43.9%

Files with Coverage Reduction	New Missed Lines	%
active/active.go	2	90.63%

Totals
Change from base Build 7057:	-0.6%
Covered Lines:	3946
Relevant Lines:	6201

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💛 - Coveralls

[stephen-soltesz]

Closing old PR - and referencing the notes from this change in #1085