Add LICENSE to Windows installer, fix filename extensions and update URL.

Add the LICENSE file to the Windows installer, change installed filename
extensions from .rtf to .txt (assume a text editor is installed that
understands LF) and fix the "update url" to be http://bluestop.org/fio/
since that's where new Windows installers are.

Signed-off-by: Jens Axboe <axboe@kernel.dk>