Upgrade notifier tray icon
--------------------------

This is a small tray icon that backgrounds itself and checks for
upgrades. It must be ensured by other means (like a cron job) that a
regular "apt-get update" is done. This is ensured by installing a
option into /etc/apt/apt.conf.d to trigger a cron update script.

It uses the following file from the apt package for the updating
of the package information:
  /etc/cron.daily/apt

The following files are installed as part of the update-notifier-common
package and trigger regular the /etc/cron.daily/apt job:
  /etc/apt/apt.conf.d/10periodic
  /etc/apt/apt.conf.d/20archive

The "10periodic" file controls how often (in days) certain actions are
run. The most common one is: APT::Periodic::Update-Package-Lists is
used for the "apt-get update". The header of /etc/cron.daily/apt
contains more information of the individual options.

The "20archive" file controls the packages (.deb) cache in
/var/cache/apt/archives - it can be used to define a maximum total
size for the deb files there and the time (in days) until they get
deleted. See the header of /etc/cron.daily/apt for more details.

It uses GIO to monitor /var/lib/apt/lists/* and
/var/lib/update-notifier/dpkg-run-stamp. If they change it updates
it's status.

It also supports interactive hooks and reboot notification support,
see HOOKS for details.

It will detect if a new distribution CD is inserted.

Additionally it has grown avahi and crash report collection
support. Both are Ubuntu specific.

Based on ideas of Matt Zimmerman und Jeff Waught. Tray example from
Lukas Lipka <lukas@pmad.net>. Lot's of cleanups from Michiel Sikkes.
Thanks!

Michael Vogt
