Allow to set API icons in @Api + use new Google logo

[clementdenis]

The new logo is coming from the default icon in the public API Explorer

[codecov-io]

Codecov Report

Merging #122 into master will decrease coverage by 0.14%.
The diff coverage is 48%.

@@             Coverage Diff             @@
##             master    #122      +/-   ##
===========================================
- Coverage     79.75%   79.6%   -0.15%     
- Complexity     1652    1658       +6     
===========================================
  Files           156     156              
  Lines          5536    5561      +25     
  Branches        710     713       +3     
===========================================
+ Hits           4415    4427      +12     
- Misses          843     851       +8     
- Partials        278     283       +5

Impacted Files	Coverage Δ	Complexity Δ
...e/api/server/spi/discovery/DiscoveryGenerator.java	85.85% <0%> (-1.71%)	51 <0> (ø)
...server/spi/config/jsonwriter/JsonConfigWriter.java	66.55% <0%> (-1.11%)	48 <0> (ø)
...ig/annotationreader/ApiConfigAnnotationReader.java	94.53% <100%> (+0.06%)	48 <0> (ø)	⬇️
.../google/api/server/spi/config/model/ApiConfig.java	94.85% <100%> (+0.24%)	73 <4> (+4)	⬆️
...i/config/annotationreader/ApiAnnotationConfig.java	82.6% <33.33%> (-3.44%)	50 <2> (+2)

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[tangiel]

Hey @clementdenis, thanks for the PR! Unfortunately, I have been told that the icon customization is on the deprecation path, so we shouldn't allow customization. But if you want to include the change to the new logo, I'm fine with it.

[clementdenis]

Hi @tangiel, I submitted a #131 with only the change to the default Google icon, you can close this one.
It's a bit sad this feature is getting deprecated, for example we have about 20 APIs in a single App Engine project, having different icons in the API explorer would be really great.

[tangiel]

Thanks as always, Clement. I forwarded your feedback to the API Explorer team.