Add buttons for changing preferences to group and person templates

aleksis/core/templates/core/group_full.html

 {# -*- engine:django -*- #}
 
 {% extends "core/base.html" %}
+{% load rules %}
 
 {% load i18n static %}
 {% load render_table from django_tables2 %}
@@ -9,12 +10,26 @@
 
 {% block content %}
   <h4>{{ group.name }} <small class="grey-text">{{ group.short_name }}</small></h4>
-  <p>
-    <a href="{% url 'edit_group_by_id' group.id %}" class="btn waves-effect waves-light">
-      <i class="material-icons left">edit</i>
-      {% trans "Edit" %}
-    </a>
-  </p>
+
+  {% has_perm 'core.edit_group' user group as can_change_group %}
+  {% has_perm 'core.change_group_preferences' user group as can_change_group_preferences %}
+
+  {% if can_change_group or can_change_group_preferences %}
+    <p>
+      {% if can_change_group %}
+        <a href="{% url 'edit_group_by_id' group.id %}" class="btn waves-effect waves-light">
+          <i class="material-icons left">edit</i>
+          {% trans "Edit" %}
+        </a>
+      {% endif %}
+      {% if can_change_group_preferences %}
+        <a href="{% url "preferences_group" group.id %}" class="btn waves-effect waves-light">
+          <i class="material-icons left">settings</i>
+          {% trans "Change preferences" %}
+        </a>
+      {% endif %}
+    </p>
+  {% endif %}
 
   <h5>{% blocktrans %}Owners{% endblocktrans %}</h5>
   {% render_table owners_table %}

aleksis/core/templates/core/person_full.html

@@ -11,12 +11,23 @@
   <h4>{{ person.first_name }} {{ person.last_name }}</h4>
 
   {% has_perm 'core.edit_person' user person as can_change_person %}
-  {% if can_change_person %}
+  {% has_perm 'core.change_person_preferences' user person as can_change_person_preferences %}
+
+  {% if can_change_person or can_change_person_preferences %}
     <p>
-      <a href="{% url 'edit_person_by_id' person.id %}" class="btn waves-effect waves-light">
-        <i class="material-icons left">edit</i>
-        {% trans "Edit" %}
-      </a>
+      {% if can_change_person %}
+        <a href="{% url 'edit_person_by_id' person.id %}" class="btn waves-effect waves-light">
+          <i class="material-icons left">edit</i>
+          {% trans "Edit" %}
+        </a>
+      {% endif %}
+
+      {% if can_change_person_preferences %}
+        <a href="{% url "preferences_person" person.id %}" class="btn waves-effect waves-light">
+          <i class="material-icons left">settings</i>
+          {% trans "Change preferences" %}
+        </a>
+      {% endif %}
     </p>
   {% endif %}