This allows users to load a different configuration file instead of the
default config.ini. It works in combination with other configuration
actions, like --config and --create-config.

Ref T529

This supports running the server on port 443, serving secure pages, with
automatic redirects from the insecure site. It also modifies the
configuration process to better guide users through configuring for
running behind a reverse proxy or as a standalone server.

This closes T537

- Database schema changes, removing obsolete custom domain-related code
- Missing user structs
- Setup verbiage changes
- Missing routes
- Missing error messages

Plus update copy / options / templates in the config process.

This adds a new --config flag and rearranges some config fields.