This reduces the confusion with the nixos/modules/deployment.nix module,
and should make it clearer that it can contain any configuration that
applies to all hosts on the grid.

Using AWS is what causes it so using AWS can be what fixes it, too.

... This breaks the tie, thx to https://github.com/DBCDK/morph/issues/146

Just require hostName and domain instead of an extra publicIPv4 option.  Leave
behind a similar option, `publicAddress`, just in case it needs to be
overridden at some point, but stop supplying a value for it anywhere.

Put its contents in it and then use them from there instead of importing them
all over the rest of the code.

The default case was actually catastrophically bad for any actual deployment
since it would just lock everyone out of all the systems.

More flexibility and less dots in config files.
Implements #65.

Discern make-issuer.nix from issuer.nix better.