[notification] drop on commit sending of message feature of NotificationView
It duplicates feature already provided by
cw.hooks.notification.notify_on_commit function.
Simplify the API on the way.
[datafeed parser] fix retrieve_url to always return urllib2.urlopen compatible output
as one should expect to be able to call geturl/getcode/info on the returned
object whatever the url he gave.
Related to #3682069