in PuSH/FeedsHTTPFetcher callbacks.

Issue #1418382: Fixed unsubscribe requests to PuSH hubs failing due to transaction in node_delete().

- DRUPAL-7--1-0-alpha2 http://github.com/lxbarth/feeds/tree/DRUPAL-7--1-0-alpha2
and
- DRUPAL-7--2-0-alpha1 http://github.com/lxbarth/feeds/tree/DRUPAL-7--2-0-alpha1

  language, user properties from parent feed node. Note: Signatures of
  FeedsProcessor::map(), existingItemId(), FeedsParser::getSourceElement()
  changed.

Fix accidental roll back of previous commit 'Stop PubSubHubbub from subscribing if it is not enabled.'

Basic auth can be used by supplying URLs like http://user:pw@example.com/feed .
The authentication in URL approach is powerful enough for most use cases. The only advantage
that the UI that is about to be removed here would have had is that it could change
basic auth credentials for a series of feeds in a single spot. Will post this patch
on the issue queue for further consideration.

Throw exception when download fails.