Added authorization template

[mangchiandjjoe]

Release note:

Authorization adapter template.
Any authorization module needs to answer the question: Is a “subject” allowed to do an “action”. 

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[istio-merge-robot]

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[codecov[bot]]

Codecov Report

Merging #1458 into master will increase coverage by <.01%. The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1458      +/-   ##
==========================================
+ Coverage   84.65%   84.65%   +<.01%     
==========================================
  Files         122      122              
  Lines       11922    11922              
==========================================
+ Hits        10092    10093       +1     
+ Misses       1634     1633       -1     
  Partials      196      196

Impacted Files	Coverage Δ
adapter/stackdriver/metric/bufferedClient.go	90% <0%> (-2.5%)	:arrow_down:
tools/codegen/pkg/inventory/generator.go	71.87% <0%> (+6.25%)	:arrow_up:

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[mangchiandjjoe]

@geeknoid @douglas-reid @mandarjog @guptasu @ZackButcher @liminw

Could you please review the PR?

[geeknoid]

I started a conversation about auth templates here: https://groups.google.com/forum/#!topic/istio-integrations/hWPkl95MmHM

Let's discuss there for a while.

Thanks.

[geeknoid]

This repo is no longer accepting PRs. Please resubmit this change to the istio/istio repo.

Thanks.