[UBUNTU] Improve handling of maintainer fields, support original-maintainer

[UBUNTU] Improve handling of maintainer fields, support original-maintainer

Handle and display Original-Maintainer field contents. Also treat
Uploaders as being related to Original-Maintainer if that exists
since AFAICT Ubuntu doesn't use this field.

Don't show the email addresses for Original-Maintainer, since they are
usually not needed anyway.

Add some helpful suggestions below maintainer email addresses to file
bugs or questions in launchpad instead. Usually this should give a
better response.

With thanks to Colin Watson <cjwatson -at- ubuntu com> for nagging
and suggestions.