Log Message:
py-gunicorn: Add ALTERNATIVES and adjust PLIST for multi-packages support

- Install bin/gunicorn and bin/gunicorn_paster with the PYVERSSUFFIX appended at
  the end in order to be used by both Python 2 and a Python 3 package
- Adjust PLIST for bin/gunicorn{,_paster} and for all the files installed as
  part of DOCDIR and EXAMPLESDIR

PKGREVISION++