Add new dplint frontend to support "git-like" Lintian commands

Signed-off-by: Niels Thykier <niels@thykier.net>
Turn lintian-info into a dplint command

Signed-off-by: Niels Thykier <niels@thykier.net>
d/changelog: Add entries for dplint + commands/info

Signed-off-by: Niels Thykier <niels@thykier.net>
lintian: Deprecate --root/LINTIAN_ROOT

Replace --root/LINTIAN_ROOT with a small bit of logic to determine the
correct LINTIAN_ROOT when run from an exacted source package.

Signed-off-by: Niels Thykier <niels@thykier.net>