General cleanup of the packaging files

General cleanup of the packaging files

* Update debhelper compatibility level to V7.
  - Use debhelper rule minimization.
* Drop specific version from Perl build dependency, since it was older
  than the version in stable.
* Lower the priority to extra to match Heimdal.
* Set myself as maintainer since I'll be doing the Debian uploads.
* Add Vcs-Git, Vcs-Browser, and Homepage control fields.
* Reformatting and improvements of binary package description.
* Update standards version to 3.8.4.