Add instance settings.

Addresses: #58

Currently implemented:

* Instance name
* Instance description
* Code of conduct
* Allow registration

I decided to store this in the database so that settings can be easily
changed at runtime through the web interface. (This web interface does
not exist.)

fedireads/templates/about.html

@@ -0,0 +1,21 @@
+{% extends 'layout.html' %}
+{% block content %}
+<div class="content-container">
+    <h2>About {{ site_settings.name }}</h2>
+    <p>
+    {{ site_settings.instance_description }}
+    </p>
+
+    <p>
+    <small>
+    <a href="/login/">Login or Create an Account</a>
+    </small>
+    </p>
+
+    <h2>Code of Conduct</h2>
+    <p>
+    {{ site_settings.code_of_conduct }}
+    </p>
+
+</div>
+{% endblock %}

fedireads/templates/login.html

@@ -1,7 +1,20 @@
 {% extends 'layout.html' %}
 {% block content %}
-<div class="row">
 
+<div class="content-container">
+    <h2>About {{ site_settings.name }}</h2>
+    <p>
+    {{ site_settings.instance_description }}
+    </p>
+
+    <p>
+    <small>
+        <a href="/about/">More about this site</a>
+    </small>
+    </p>
+</div>
+
+<div class="row">
 <div class="content-container login">
     <h2>Create an Account</h2>
     <p><small>
@@ -9,6 +22,7 @@
         friends here and on any other federated server, like Mastodon and PixelFed.
     </small></p>
 
+    {% if site_settings.allow_registration %}
     <div>
         <form name="register" method="post" action="/register">
             {% csrf_token %}
@@ -16,6 +30,12 @@
             <button type="submit">Create account</button>
         </form>
     </div>
+    {% else %}
+
+    <small>
+    This instance is not open for registration.
+    </small>
+    {% endif %}
 </div>
 
 <div class="content-container login">