Standardize how nginx gets started and switches users.

Now the web nginx instance (like the router instance) starts as root,
and then handles its user switching internally.

Aside from standardizing things, this also help fix weird logs about
failing to write to the hardcoded error.log file (despite our settings
which should mean that file is never used).
Remove unused nginx ssl.conf include file.

This got integrated into router.conf.hbs a while ago.
Setup to allow the default install to respond to any host.

Now an out of the box install will by default respond to any hostname
(so it's only with additional configuration that the hosts become more
specific).

Related to this, the app now generates a self-signed SSL certificate for
hosting purposes if one is not supplied. This is not what a real
environment would use, but useful for initial development environments
(without having to completely disable SSL there).