Add check for bots, spiders to prevent impressions

[kookster]

@kookster commented on Sun Dec 13 2015

Use some known list, plus additions from log analysis and testing

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@kookster commented on Thu Feb 11 2016

I added the lib for this, but not the depression logging integration.

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@cavis commented on Tue May 23 2017

Note: this still isn't implemented.

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@cavis commented on Thu Sep 07 2017

May be some question if this should live in DT or the Lambda now. But should be pretty easy either way. (The prx-podagent project used by Lambda already detects bots).