13. core: Add authentication module

This patch adds a new "authentication" backend module intended to
contain the builtin authentication and directory implementations.

In this initial version it only contains very simple NOP authenticator
and an equally simple NOP directory. The NOP authenticator just accepts
any user name and any password, without validation. The NOP directory
doesn't have any backend, it just creates users as requested. Obviously
these aren't very useful outside of testing, althought the NOP directory
can be useful when authentication is relevant but user details (mail,
name, etc) and groups aren't relevant

In order to use these authenticator and directory a new authentication
profile has to be configured creating a nop.conf file inside
/etc/ovirt-engine/auth.conf.d. The content of that file should be
something like this:

  #
  # The name of the authentication profile (this is what will be
  # displayed to the user in the login dialog):
  #
  name=nop

  #
  # The name of the JBoss module that contains the implementation of the
  # authenticator and the directory:
  #
  module=org.ovirt.engine.core.authentication

  #
  # The type is used to select the implementation of the authenticator
  # and the directory. The NOP authenticator and directory register
  # themselves with "nop" as the type:
  #
  type=nop

Change-Id: I79ff506bfca42d90a1fbaa7d9bfa8b0c4c140dff
Signed-off-by: Juan Hernandez <juan.hernandez@redhat.com>