New feature in trunk:
URL('index',args=[],vars={},hash_key='xxx')
the URL will have a _signature attached. The associated controller can
check for the signature with
def index():
if not URL.verify(hmac_key='xxx'): ......
...
Please test it. In particular we need to test the workflow and see if
we are missing something useful or doing something wrong.
Thanks Brian Meredyk
