add new "apt-get upgrade --with-allow-new" option

The --with-allow-new option maps to APT::Get::UpgradeAllowNew and
will allow "apt-get upgrade" to install new packages (but not to
delete existing packages)
add man-page, improve option, use --with-new-pkgs as the flag
its --with-new-pkgs
Merge remote-tracking branch 'upstream/debian/sid' into feature/upgrade-with-new
rename "--dpkg-progress" to "--show-progress" and document it in apt-get.8
add -o DpkgPM::Progress-Fancy for better dpkg progress output on vt100+ terminals
use Dpkg::Progress-Fancy to be consitent with Dpkg::Progress
fix off-by-one error in pkgDPkgPM::SetupTerminalScrollArea()
Merge remote-tracking branch 'mvo/feature/dpkg-progress-docs' into debian/sid
Merge remote-tracking branch 'mvo/feature/upgrade-with-new' into debian/sid
Merge remote-tracking branch 'mvo/feature/dpkg-progress-fancy' into debian/sid
prepare new release