Remove parent and url values in streamer and notifications

In the past our live-updater added some extra values (like parent data, titles)
for our annotations because the client-side used them.

Now we do not use any, so there is no point in doing that.
Notifications use parent data, but it now passed as extra data, instead of being
part of the annotation.

Fixed datetime issues within our reply-notification template
Merge pull request #1504 from hypothesis/1498-parent-values-in-streamer

Remove parent and url values in streamer and notifications