Include AUTHORS in release package.

Include AUTHORS in release package.

Fixes Bug #976267.

Include AUTHORS file in release package. The file is generated
automatically from git. Handle different combination for mailmap
records. Include test case to verify this fix.

* MANIFEST.in
  Include AUTHORS file in release package.

* .gitignore
  Add AUTHORS file.

* quantum/openstack/common/setup.py
  generate_authors(): New method to create AUTHORS file. If
  AUTHORS.in file exists, append it's content to AUTHORS file.
  parse_mailmap(): Handle all mailmap combination while parsing.

* setup.py
  Import the new method.
  Generate AUTHORS file before creating the package.

* quantum/tests/unit/test_setup.py
  New test script to verify different combination of records
  in mailmap file.

Change-Id: I220e8a20c96d37df3fa2ba0424e8372496e67895