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

Ref T529

Ref T529

This extracts the LEFT/SUBSTR logic into its own datastore.clip() method
that also works correctly with SQLite.

Ref T529

We store times in UTC in all other places, but the post.Created logic
when creating a post meant that dates were being stored in a user's
local timezone. This fixes that.

Ref T529

The formatted string was invalid before, causing date parsing to fail.
This fixes that.

Ref T529

Ref T529

This also moves the stats database logic out of nodeinfo.go and into
database.go.

We load it always, no need for a user config UI

This is a first stab at having a configurable code highlighting option,
similar to the MathJax rendering option. This change makes a checkbox
in the settings for code highlighting using the highlightjs.org
library.
What works: code highlighting in multi-user env is like I would
expect. single and anon(?) needs work

Things to resolve/consider:
- does the .IsCode test for code highlighting need to stay? At least
this and that should use the same version of the highlight.js lib.
- can the common templating part be 'included' somehow?
- the anon vs single-user vs multi-user code is not completely
clear (to me)
- bring js to local instead of cloudfare cdn (perhaps combine with
MathJax)

This allows admin to edit these pages from the web, using Markdown. It
also dynamically loads information on those pages now, and makes loading
`pages` templates a little easier to find in the code / more explicit.

It requires this new schema change:

CREATE TABLE IF NOT EXISTS `appcontent` (
  `id` varchar(36) NOT NULL,
  `content` mediumtext CHARACTER SET utf8 COLLATE utf8_bin NOT NULL,
  `updated` datetime NOT NULL DEFAULT CURRENT_TIMESTAMP,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1;

This closes T533

This helps with post importing and clients that want to support post
scheduling. It also changes how Collection.ForPublic() works, no longer
resetting the ID.

Closes T532

This now sends out a `Create` activity when a post is moved from a draft
to a blog.

This closes #9. Closes T526.

This closes #28

This closes #7

- view_count

This closes #7

This fixes MySQL errors about missing default values.

This allows logging in with a non-normalized username.

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

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