Fix install of php5-cgi, roundcube SQL directory on Ubuntu 14.04

Not sure if I've tested this. Also because of graylisting there's not much of a need
to do sophisticated spam filtering, at least based on the email I get.

DNS test: also check a public nameserver to verify that the registrar (or up-host) configuration is correct too

remove apache before installing nginx --- it's not needed and will start complaining about the port being in use, or it might interfere with nginx

When I re-did this, I left in an old reference to the php-fcgid
script that never made it into the repo. Deleting that and moving
the php-fcgid configuration on top of it.

fixes #9
see 2ebd9706

remove old Amazon EC2-related things since no one should ever deploy a mail server to EC2 (IPs have bad reputation)

update how we get the missing roundcube SQL directory: not sure previous URL was correct, should also match the deb version

add php-fastcgi init script to start the FastCGI process needed to run Roundcube (and any other PHP scripts, really)

Documentation fixes

In your domain name.

Was linking to the wrong path/filename

set the postfix helo string to the machine's hostname, overriding the Debian default 'localhost', since some MTAs require a hostname there

generate a self-signed certificate for PUBLIC_HOSTNAME and change DNS MX records to PRIMARY_HOSTNAME so it matches

set the DNS SOA RNAME domain contact email to hostmaster@PRIMARY_HOSTNAME and add an alias when creating the first mail user

Credit @shevski for early conversations around decentralizing email.

mwhahahaha