clean up BSD license so it's recognized by GitHub auto detection

Author: mythz

LICENSE.txt renamed to LICENSE

@@ -1,6 +1,5 @@
 Copyright (c) 2007-present, Demis Bellot, ServiceStack, Inc.
 https://servicestack.net
-All rights reserved.
 
 Redistribution and use in source and binary forms, with or without
 modification, are permitted provided that the following conditions are met:
@@ -9,7 +8,7 @@ modification, are permitted provided that the following conditions are met:
     * Redistributions in binary form must reproduce the above copyright
       notice, this list of conditions and the following disclaimer in the
       documentation and/or other materials provided with the distribution.
-    * Neither the name of the ServiceStack nor the
+    * Neither the name of the copyright holder nor the
       names of its contributors may be used to endorse or promote products
       derived from this software without specific prior written permission.