added overall readme file

README.txt

+README 	
+
+AUTHORS
+    Claudio Mandiroli (claudio.mandrioli@control.lth.se)
+
+THANKS
+    Thanks to Isaac Skog (skog@kth.se) the author of the 'sensor fusion' part of the
+    code on top hos which has been implemented the 'GPS modeling' part.
+    
+INSTALL
+    
+
+COPYING / LICENSE 	Copyright and licensing information
+