Group email notifications into the same thread (per topic)

Other services, like Github, use the same subject for their email notifications about the same issue or pull request. This allows to see all emails in the same thread in gmail and clients that support grouping by thread/conversation. This is quite convenient to keep you inbox cleaner.

In order to do this, UserEcho would only need to use the same subject for all the notification emails about the same topic.

So instead of:

    [Project / Forum] New feedback "some topic"

And:

    [Project / Forum] New comment for "some topic"

There would be a single subject like:

    [Project / Forum] "some topic"

With the first lines of the email describing the action that happened over it "New feedback created", "New comment added for this topic", etc.

Alternatively, being able to customize the subject (I know footer and from already are) would provide the functionality I need, but I think it'll be a better default behavior for UserEcho nevertheless.