Replaced fallback file for unattended-upgrades

with a decent one for wheezy onwards. The main syntax shouldn't
change, hopefully, from now on. It's a very basic generic one,
that uses variables for Distribution/Codename and should apply
to all coming distributions.

Removed from the default 50unattended-upgrades
----------------------------------------------

- APT::Periodic::Update-Package-Lists "1";
- APT::Periodic::Unattended-Upgrade "1";
cause this is not something the unattended upgrades class should
set by default.

- APT::UnattendedUpgrades::LogDir "/var/log/";
- APT::UnattendedUpgrades::LogFile "unattended_upgrades.log";
Because we shouldn't change the default logdest by default, which
is /var/log/unattended_upgrades/*.

- Blacklist for linux-image*, because this we shouldn't blacklist
  packages by default.
50unattended-upgrades: lenny version
50unattended-upgrades: squeeze version
50unattended-upgrades: ubuntu precise version
50unattended-upgrades: ubuntu quantal, symlink to precise
from Ubuntu oneiric (11.10) on, the 50unattended-upgrades default can be used
refactor 50unattended-upgrades default file

The syntax is valid from v0.70 on (Debian Wheezy, Ubuntu Oneiric
and later).
It includes Unattended-Upgrade::Origins-Patterns both for Debian
and Ubuntu, which even work on systems with both package sources
enables. On Debian- or Ubuntu-only systems it doesn't hurt to have
both Patterns included.
use oldstable for lenny, force unattended upgrades
squeeze: use colon seperator to be able to include backport updates,

also force unattended upgrades
use codename instead of archive variable for Debian
forgot ${distro_codename}-updates in 50unattended-upgrades fallback
Merge remote-tracking branch 'leap/feature/unattended_upgrades' into review

Conflicts:
	files/lenny/50unattended-upgrades