debian_installer: install avahi-daemon
debian_installer: assert that /dev/sd* exists rather than ./sd*
debian_installer: dist-upgrade multiple times

For some reason if dist-upgrade is run only once the updates are often
incomplete. By forcing it to run 3 times this problem is (hopefully)
worked around.
debian_installer: update login for creating 32bit symlinks

This makes two changes:
1) it only tries to create the symlink if the bare .so doesn't exist
2) it looks for both a so.1 and a so.0 to link to .so
debian_installer: modify logind.conf to not handle lid events
debian_installer: update some comments
debian_installer: fix bugs in finalize.sh

- fix avahi-daemon install (mis-spelled package name)
- run apt-get autoremove after the updates and installs finish
Merge pull request #9 from dcbaker/wip/installer-cleanups

Wip/installer cleanups