This adds new configuration values that specify the parent directory of
application resources:

- templates_parent_dir
- static_parent_dir
- pages_parent_dir
- keys_parent_dir

For any values not specified, the application will default to the
current directory.

This closes T560

This includes:

- A new `user_invites` config value that determines who can generate
  invite links
- A new page for generating invite links, with new user navigation link
- A new /invite/ path that allows anyone to sign up via unique invite
  link, even if registrations are closed
- Tracking who (of registered users) has been invited by whom

It requires an updated database with `writefreely --migrate` in order to
work.

This closes T556

This adds a "Reader" section of the site for admins who want to enable
it for their instance. That means visitors can go to /read and see who
has publicly shared their writing. They can also follow all public posts
via RSS by going to /read/feed/. Writers on an instance with this
`local_timeline` setting enabled can publish to the timeline by going
into their blog settings and choosing the "Public" visibility setting.

The `local_timeline` feature is disabled by default, as is the Public
setting on writer blogs. Enabling it adds a "Reader" navigation item and
enables the reader endpoints. This feature will also consume more
memory, as public posts are cached in memory for 10 minutes.

These changes include code ported over from Read.Write.as, and thus
include some experimental features like filtering public posts by tags
and authors. These features aren't well-tested or complete.

Closes T554

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

Ref T529

This changes what displays in the NodeInfo, and in the future might be
used for other things.

Minimal changes, definitely WIP, to resolve:

- how to support dualstack when not using localhost?
- net/http package uses string, mentions IP address instead of bind,
  need info.

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

This also includes a new Dev config options

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

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

Includes new instance stats and the new option to show user stats, as
well.

This includes config changes, collections, posts, some post rendering
funcs, and actual database connection when the server starts up.

Includes app config and some initialization