added logout button

src/main/resources/templates/template.html

@@ -33,6 +33,7 @@
         <ul class="navbar-nav">
           <li><a class="nav-link active" th:href="@{/dashboard}">Startseite</a></li>
         	<li layout:fragment="left" class="left">TODO: left menu integration</li>
+        	<li><a class="nav-link" th:href="@{/logout}">Abmelden</a></li>
         </ul>
       </nav>
     </div>