New Gitea installations will now use LDAP authentication, typically
provided by the included `lldap` service, over SMTP authentication, as
this is is more flexible.
This commit adds a new service for Gitea, exposing HTTP and SSH ports by
default (SSH over 7920), and accepting authentication via the local SMTP
server. No users are otherwise created by default, and administration is
expected to happen either via CLI, or via a custom admin user.
