[ADD #530] extended About dialog

src/gui/qt4/OpenWalnutAbout.html

 <h1>OpenWalnut</h1>
+OpenWalnut is an open source tool for multi-modal medical
+and brain data visualization. Its universality allows it
+to be easily extended and used in a large variety of application
+ cases. It is both, a tool for the scientific user and a
+ powerful framework for the visualization researcher. 
+ OpenWalnut is licensed under the terms of the GNU Lesser 
+ General Public License. Written entirely in Standard C++ 
+ and using a number of portable libraries (e.g.  OpenSceneGraph and  Qt)
+ it runs on all Windows platforms, OSX and GNU/Linux operating systems. <br />
+   <br />
 Copyright 2009-2011 OpenWalnut community, BSV@Uni-Leipzig, and 
 CNCF@MPI-CBS. For more information see 
 <a href="http://www.openwalnut.org/copying">http://www.openwalnut.org/copying</a>.<br><br>
@@ -7,13 +17,13 @@ This is free software, and you are welcome to redistribute it
 under the terms of the GNU Lesser General Public License. 
 You should have received a copy of the GNU Lesser General Public License 
 along with OpenWalnut. If not, see 
-&lt;<a href="http://www.gnu.org/licenses">http://www.gnu.org/licenses</a>&gt;.<br>
+&lt;<a href="http://www.gnu.org/licenses">http://www.gnu.org/licenses</a>&gt;.
 
 <h4>Contact</h4>
 Website: <a href="http://www.openwalnut.org">http://www.openwalnut.org</a><br>
 Email: <a href="mailto:contact@openwalnut.org">contact@openwalnut.org</a>
 
-<h4>Contributors up to version 1.2:</h4>
+<h4>Contributors up to version 1.2</h4>
 <i>(in alphabetical order, current administrators in bold font)</i><br>
 Dirk Albrecht, <b>Sebastian Eichelbaum</b>, Robert Frohl, <b>Mathias Goldau</b>, Christian Heine, 
 Mario Hlawitschka, Sebastian Kiunke, Robin Ledig, Cornelius Mueller,