Adding new Google+ scraper bot

[jaydiablo]

Fixes #1415.

I looked back through our logs from 2013 - today looking for various versions of this google bot, and only found 4 different useragents:

Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/56.0.2924.87 Safari/537.36 Google (+https://developers.google.com/+/web/snippet/)
Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/49.0.2623.75 Safari/537.36 Google (+https://developers.google.com/+/web/snippet/)
Mozilla/5.0 (Windows NT 6.1; rv:6.0) Gecko/20110814 Firefox/6.0 Google (+https://developers.google.com/+/web/snippet/)
Mozilla/5.0 (Windows NT 6.1 rv:6.0) Gecko/20110814 Firefox/6.0 Google (+https://developers.google.com/+/web/snippet/)

The two Gecko ones are already covered by tests, and the first two Webkit ones are covered by the new test I added.

The other platforms of this bot could probably be removed, but I left them there just in case.

[jaydiablo]

Oops, forgot to test Lite/Standard, will fix.

[codecov]

Codecov Report

Merging #1422 into master will increase coverage by <.01%.
The diff coverage is 75%.

@@             Coverage Diff              @@
##             master    #1422      +/-   ##
============================================
+ Coverage     33.48%   33.49%   +<.01%     
  Complexity      816      816              
============================================
  Files          1433     1433              
  Lines         53615    53619       +4     
  Branches      21035    21036       +1     
============================================
+ Hits          17955    17959       +4     
  Misses        35660    35660

Impacted Files	Coverage Δ	Complexity Δ
...ser-agents/crawlers/google/google-web-snippet.json	34.78% <75%> (+13.72%)	0 <0> (ø)	⬇️

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