This is a cherry-pick of PR#4223:
- Add script to create debian source package
- Update debian metadata based on Debian repos
- Remove some lintian warnings and errors
- Remove support Xenial
- Reduce size of icon
- Omit confusing values from gbp.conf
This change fixes the launchpad build script and also improves
updating the watch file.
If we use the variables that uscan provides we don't have to
hard-code the package name in the watch file. This makes it possible
to use a generic one for all packages.
