Sign the debian apt package files and add new makefile targets.

* Change the maintainer to 'TMI Packages <pgks@titaniummirror.com>'.
* Sign the packages with the maintainer key.  The current user must have the
  secret key for the maintainer.
* Add a pbuilder makefile target that builds the package via pbuilder, pulls
  the results files to the build dir, and signs them.
* Add a release makefile target that, with a properly configured ~/.dput.cf,
  will release the built package to the apt repository.