Fixes #8499 - Link LICENSE from README

I think this statement should be moved to LICENSE, and made clear that it refers to the "Foreman" part of the application, e.g.

<pre>
The Foreman repository/package is licensed under the GNU GPL v3 or newer,
with some exceptions.

Copyright (c) 2009-2014 to the respective authors

All copyright holders for the Foreman project are in the separate file called
Contributors.

Except where specified below, this program and entire repository is free
software: you can redistribute it and/or modify it under the terms of the GNU
General Public License as published by the Free Software Foundation, either
version 3 of the License, or any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program.  If not, see <http://www.gnu.org/licenses/>.

The following files and directories are exceptions:

* app/views/unattended/ztp/provision.erb is under 2-clause BSD license
* config/locales/ and public/blank.html are MIT licensed
* lib/tasks/convert.rake is under Revised BSD license
* extras/noVNC/websockify is LGPL v3 licensed
* vendor/assets/fonts/ is ASL 2.0 licensed
* vendor/assets/javascripts/ace/ is under Revised BSD license
* vendor/assets/javascripts/noVNC/ is LGPL v3, GPL v2+, MIT and BSD
* vendor/assets/javascripts/diff.js is under Revised BSD license
* vendor/assets/javascripts/jquery.cookie.js is GNU GPL v2/MIT licensed
* vendor/assets/javascripts/jquery.dataTables.min.js is GNU GPL v2/BSD
* vendor/assets/javascripts/jquery.jeditable.js is MIT licensed
* vendor/assets/javascripts/jquery.jnotify.js is ASL 2.0 licensed

Holders for code listed above are:

  (c) 2013, Juniper Networks
  (c) 2008, Matson Systems, Inc.
  (c) 2010, Ajax.org B.V.
  (c) 2005, Brad Neuberg, bkn3@columbia.edu
  (c) 2009-2011, Kevin Decker <kpdecker@gmail.com>
  (c) Hiroshi Ichikawa <http://gimite.net/en/>
  (c) Martijn Pieters <mj@digicool.com>, Samuel Sieb <samuel@sieb.net>
  (C) 1999 AT&T Laboratories Cambridge
  (c) 1996 Widget Workshop, Inc.
  (C) 1996 by Jef Poskanzer <jef@acme.com>
  (c) 2010 Klaus Hartl (stilbuero.de)
  (c) 2008-2012 Allan Jardine
  (c) 2006-2009 Mika Tuupola, Dylan Verheul
  (c) 2010 Giva, Inc.

All rights reserved.
</pre>