Use context processor to include site settings in templates

bookwyrm/templates/login.html

@@ -36,7 +36,7 @@
             </form>
         </div>
         <div class="box has-background-primary-light">
-            {% if site_settings.allow_registration %}
+            {% if site.allow_registration %}
             <h2 class="title">Create an Account</h2>
             <form name="register" method="post" action="/user-register">
                 {% include 'snippets/register_form.html' %}
@@ -50,7 +50,7 @@
 
     <div class="column">
         <div class="block">
-            {% include 'snippets/about.html' with site_settings=site_settings %}
+            {% include 'snippets/about.html' %}
 
             <p class="block">
                 <a href="/about/">More about this site</a>