Add support for web requests to fetch status with a path.

This changes the format of the web request result to include more
information (especially revision) reguardless of the path requsted.

{
  'revision': <int>,
  'url': <status_url_requested>,
  'status': <contents of the status tree at the requested URL>
}

The valus sent to status deferreds are now a dictionary of the same
format as the new web requests.

Moved web handler URL for status from:
  http:<server>/status_handler -> http:<server>/status

Status.createNotification renamed -> Status.deferred.

Status.deferred accepts a default status url of 'status://', and None
is no longer accepted at all.

Normallized status url naming to url, not url.

StatusDeferred moved to a member of Status named _StatusDeferred.