Add documentation link in discovery files

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[codecov-io]

Codecov Report

Merging #121 into master will increase coverage by 0.04%. The diff coverage is 100%.

@@             Coverage Diff              @@
##             master     #121      +/-   ##
============================================
+ Coverage     79.75%   79.79%   +0.04%     
- Complexity     1652     1654       +2     
============================================
  Files           156      156              
  Lines          5536     5538       +2     
  Branches        710      711       +1     
============================================
+ Hits           4415     4419       +4     
+ Misses          843      842       -1     
+ Partials        278      277       -1

Impacted Files	Coverage Δ	Complexity Δ
...e/api/server/spi/discovery/DiscoveryGenerator.java	87.68% <100%> (+0.12%)	52 <0> (+1)	:arrow_up:
...i/config/annotationreader/ApiAnnotationConfig.java	88.37% <0%> (+2.32%)	49% <0%> (+1%)	:arrow_up:

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[googlebot]

CLAs look good, thanks!

[kaldebert]

I signed it!

[clementdenis]

Hi @tangiel, is there anything else we should do to have this one merged? It's actually a regression from Cloud Endpoints v1, documentationLink used to be displayed. Thanks!

[tangiel]

Nope, sorry for missing it. Thanks!