"Changeslist" on distribution series administration page is unhelpful

[Matthew Paul Thomas]

1. Go to the "Adminster" page for a distribution series.
2. In the "Changeslist" field, enter "http://ubuntu.example.com/changes.txt".

What happens: "Constraint not satisfied".

What should happen:
* The field is labelled not "Changeslist", but "E-mail changes to:".
* The caption is not "The changes list address for the distroseries" (which adds nothing), but "The mailing list or other e-mail address that Launchpad should notify about new uploads."
* When a value is entered that isn't an e-mail address, the error says not "Constraint not satisfied", but something like "This must be an e-mail address."

[Celso Providelo (cprov)]

RF 6908