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.

lib/ansible/cli/__init__.py

@@ -30,7 +30,7 @@ import getpass
 import signal
 import subprocess
 
-from ansible import __version__
+from ansible.release import __version__
 from ansible import constants as C
 from ansible.errors import AnsibleError, AnsibleOptionsError
 from ansible.utils.unicode import to_bytes, to_unicode