Squashed commit of the following:

commit ae1f68ac54cf2878d265b2bbce13bd600d2d0719
Author: Thomas Müller <thomas.mueller@tmit.eu>
Date:   Thu Aug 22 11:45:27 2013 +0200

    fixing undefined variable

commit 982f327ca10eea0a2222eae3e74210648591fd8a
Author: Thomas Müller <thomas.mueller@tmit.eu>
Date:   Wed Aug 7 12:00:14 2013 +0200

    adding login.php as alternative for index.php/login

commit da0d7e1d096fb80789524b01f0f96fe08d147943
Author: Thomas Müller <thomas.mueller@tmit.eu>
Date:   Wed Aug 7 11:36:12 2013 +0200

    adding a route for web login

commit 8e2a01160485cf7e9a2eb8bf46f06fae73956e8e
Author: Karl Beecher <karl@endocode.com>
Date:   Tue Aug 6 17:00:28 2013 +0200

    Login attempt returns true instead of exiting immediately

commit fd89d55de9e71e986e03a0de9aad9407b632e22f
Author: Karl Beecher <karl@endocode.com>
Date:   Mon Aug 5 15:31:30 2013 +0200

    Further abstraction.

    This change introduces the ApacheBackend interface for backends that
    depend on Apache authentication and session management. There are no
    longer references to specific backends in OC_User.

commit 469cfd98aea5a37985722cf5f9e00ece0ce38178
Author: Karl Beecher <karl@endocode.com>
Date:   Thu Aug 1 15:46:36 2013 +0200

    Make login attempt function protected.

commit d803515f19ff086e2028fcaa51afae579685e596
Author: Karl Beecher <karl@endocode.com>
Date:   Wed Jul 31 16:00:22 2013 +0200

    Amends the login link

    When using a Shibboleth login, clicking logout displays a message to the
    user instead of ending the session.

commit aa8c1fcea05c8268f26a10b21c4e0bc547c3414f
Author: Karl Beecher <karl@endocode.com>
Date:   Tue Jul 30 13:15:59 2013 +0200

    Abstract Shibboleth authentication into an Apache authentication method

commit 69082f2ebcab267f6e8eceb1a252f84c52236546
Author: Karl Beecher <karl@endocode.com>
Date:   Tue Jul 30 11:22:26 2013 +0200

    Convert spaces -> tabs

commit 5a80861d86855eec5906fd5e235ac4ff12efb0f2
Author: Karl Beecher <karl@endocode.com>
Date:   Mon Jul 29 17:40:48 2013 +0200

    Separate the authentication methods

    SABRE authentication and base authentication have slightly different
    workings right now. They should be refactored into a common method
    later, but time pressure requires us to reinvent the wheel slightly.

commit dc20a9f8764b103b7d8c5b713f2bcdae18708b65
Author: Karl Beecher <karl@endocode.com>
Date:   Mon Jul 29 17:07:07 2013 +0200

    Authenicate calls to WebDAV against Shibboleth.

    When using WebDAV, the OC_Connector_Sabre_Auth::authenticate method is
    normally called without trying the Shibboleth authentication... thus the
    session is not established.

    The method now tries Shib authentication, setting up a session if the
    user has already authenticated.

commit 091e4861b2246c4084c9b30e232289fde4ba1abf
Author: Karl Beecher <karl@endocode.com>
Date:   Mon Jul 29 14:04:54 2013 +0200

    Sets up the Shibboleth login attempt.

commit bae710ec0579ef99b23022cc12f6876c5fe6b0d5
Author: Karl Beecher <karl@endocode.com>
Date:   Mon Jul 29 12:36:44 2013 +0200

    Add a method for attempting shibboleth login.

    If the PHP_AUTH_USER and EPPN environment variables are set, attempt a
    Shibboleth (passwordless) login.

commit 667d0710a7854e58fb109201d9cee6ec064e793a
Author: Karl Beecher <karl@endocode.com>
Date:   Mon Jul 29 11:38:04 2013 +0200

    Revert "Adds the apps2 folder with user_shibboleth backend."

    This reverts commit 7abbdb64676d667b0c69aca37becdc47e56dc7ef.

commit 7abbdb64676d667b0c69aca37becdc47e56dc7ef
Author: Karl Beecher <karl@endocode.com>
Date:   Mon Jul 29 11:28:06 2013 +0200

    Adds the apps2 folder with user_shibboleth backend.

Conflicts:
	core/templates/layout.user.php
	lib/base.php
use $defaults instead of $theme
adding getCurrentUserId() to ApacheBackend
Merge branch 'master' into apache-auth-master
Revert "use $defaults instead of $theme"

This reverts commit d5038e93dba633cce36538905b7e5365ba1b3b63.
$defaults is not necessary here - merge artifact
code cleanup - remove special case for webdav in handleApacheAuth()
adding warning about failed apache module auth
adding PHPDoc comment
remove obsolete function login()
fixing namespace of ApacheBackend - now know as OCP\Authentication\IApacheBackend
fixing various PHPDoc comments
Also replace ApacheBackend with Authentication\IApacheBackend in user.
move call to print_unescaped() to template
Move backend finding into its own method.
Merge pull request #5072 from owncloud/apache-auth-master

OC6 Apache Authentication