recursive-include to grab spec.yaml and favicons

[jasongrout]

This backports d925e67 to pick up favicons and other files in the package distribution.

[codecov-io]

Codecov Report

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@@           Coverage Diff            @@
##             1.0.x     #347   +/-   ##
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  Coverage         ?   66.96%           
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  Files            ?       56           
  Lines            ?     5513           
  Branches         ?      716           
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  Hits             ?     3692           
  Misses           ?     1593           
  Partials         ?      228           

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[Zsailer]

Merging before tests finish, since this doesn't make any code changes.

[jasongrout]

As an explanatory note, https://packaging.python.org/guides/using-manifest-in/#manifest-in-commands notes:

Setuptools also has undocumented support for ** matching zero or more characters including forward slash, backslash, and colon.

So we should not have been using ** all along, and just used the recursive-include that is officially supported.