Fix ziploader for the cornercase of ansible invoking ansible.

* Make ziploader's ansible and ansible.module_utils libraries into
  namespace packages.
* Move __version__ and __author__ from ansible/__init__ to
  ansible/release.py.  This is because namespace packages only load one
  __init__.py.  If that is not the __init__.py with the author and
  version info then those won't be available.
* In ziplaoder, move the version ito ANSIBLE_CONSTANTS.
* Change PluginLoader to properly construct the path to the plugins even
  when namespace packages are present.

setup.py

@@ -4,7 +4,7 @@ import os
 import sys
 
 sys.path.insert(0, os.path.abspath('lib'))
-from ansible import __version__, __author__
+from ansible.release import __version__, __author__
 try:
     from setuptools import setup, find_packages
 except ImportError: