[webserver] Update urls in default data

Replace all links to sics.se with contiki.org

apps/webserver/httpd-fs/header.html

@@ -24,6 +24,6 @@
 
   <div class="contentblock">
   <p class="border-title">
-  Welcome to the <a href="http://www.sics.se/contiki/">Contiki</a> 
+  Welcome to the <a href="http://www.contiki-os.org/">Contiki</a>
   web server!
   </p>

apps/webserver/httpd-fs/index.html

@@ -24,14 +24,14 @@
 
   <div class="contentblock">
   <p class="border-title">
-  Welcome to the <a href="http://www.sics.se/contiki/">Contiki</a> 
+  Welcome to the <a href="http://www.contiki-os.org">Contiki</a>
   web server!
   </p>
 	      
 	  <p class="intro">
 	    The web pages you are watching are served by a web
 	    server running under the <a
-	    href="http://www.sics.se/contiki/">Contiki operating
+	    href="http://www.contiki-os.org">Contiki operating
 	    system</a>.
 	  </p>