Use the split argument list (slice) just for validation purposes
as it's substantially easier to do `.contains` in a string instead
of a slice. As such, pass the `configSections` arguments to
`Configure()` and check the existence of each one before showing
the options to the user.
An empty argument list is replaced by "server db app" so everything
is there negating the need to check anything else in `Configure()`.
In the same vein the default is "server db app".
The parsing is done in `app.go` alongside the other flags instead
of `main.go` as described in T657.
Add --sections flag to app.go according to T657, parse them
into a string array (check for invalid arguments and abort)
and pass them to Configure(). For now Configure() doesn't do
anything with them yet.
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.
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
Matt Baer
Michael Demetriou