Replace postfix with ssmtp.

Postfix has the problem of needing SUID, which does not work in Docker.
The process sending mail would hang on postdrop ... lacking the permissions to write the mail to disk.

ssmtp might need some config to let it sent mail to the real world...
Update /etc/apache2/conf-enabled path for ubuntu 14.04
cleanup
Set a suid bit on sudo, somehow this base image has it disabled
Elaborate docs
Use long option
Start ssh early to be able to login for debugging.