Debian package generation updates + Lintian validation fixes

  * Bump debhelper version to 9
  * Add Vcs-Hg and Vcs-Browser pointing to the git repository on github
  * Changed the license on files bundled in the debian directory to BSD-3
  * Obsolete debian/README.source removed
  * debian/source/format file added
  * close an ITP bug in the changelog
  * override the debian-watch-file-is-missing lintian warning
  * fix package description format