Canary query prototype

[gfr10598]

DRAFT - for discussion.

Decided this is a much better place to work on improving the query, so I can keep track of the changes I make. The initial commit is not too different from the original query in m-lab/analysis#12

Also tracking this query at:
https://console.cloud.google.com/bigquery?sq=581276032543:e7d8a3fd106549ebb7b00959f8068d50

I've updated a number of intermediate table names for better clarity. Also, removed some fields and commented out lines that are not needed or used.

Still needs a lot better documentation, and probably some simplification.

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This change is 

[coveralls]

Pull Request Test Coverage Report for Build 24

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 24 unchanged lines in 2 files lost coverage.
• Overall coverage decreased (-1.9%) to 53.271%

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Files with Coverage Reduction	New Missed Lines	%
pipeline/handlers.go	5	70.0%
histogram/table.go	19	75.53%

Totals
Change from base Build 11:	-1.9%
Covered Lines:	285
Relevant Lines:	535

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💛 - Coveralls