publish: Polish/refactor the publishing workflows. * Add a `--preview` option. * The `--list` option gives a nicer output, and prints warnings/errors for incorrect configuration. * Moved most of the `shell` code into a base class that's reusable. * Simplified the code to log publishing to a file. * Nicer output overall, with times.

{% extends "default.html" %}

{% block content %}
<div class="container">
    <section class="col-md-8">
    {{ content|safe }}
    </section>
    <aside class="col-md-4">
        {% include 'inc/family-sidebar.html' %}
    </aside>
</div>
{% endblock %}