EMA

* adds Ema model (basically Compensation inherited)
* adds index view for EMAs
* fixes drop-down link bug for menu 'More' in navbar
* refactors some more forms to use process_request()
* adds modified attribute to BaseResource for easy last_modified check
* adds setting of modified attribute in all places where UserAction.EDITED is added to log
* adds EMA_ACCOUNT_IDENTIFIER_LENGTH and EMA_ACCOUNT_IDENTIFIER_TEMPLATE to ema/settings.py
* adds EmaAdmin to ema/admin.py
* fixes wrong title in intervention detail view html for revocations
* adds support for subtitle variable to BaseTable and generic_index.html
* drops next_version attribute from models
* adds/updates translations
* adds default ordering for UserActionLogEntry
   * removes extra ordering in log modal rendering

templates/generic_index.html

@@ -5,12 +5,21 @@
 
 {% block body %}
     <div class="col-md">
-        {% if table.title is not None %}
-        <div class="row">
-            <h3>
-                {{ table.title }}
-            </h3>
-        </div>
+        {% if table.title %}
+            <div class="row">
+                <h3>
+                    {{ table.title }}
+                </h3>
+            </div>
+            {% if table.subtitle %}
+                <div class="row mb-2">
+                    <div class="col-lg">
+                        <small>
+                            {{ table.subtitle }}
+                        </small>
+                    </div>
+                </div>
+            {% endif %}
         {% endif %}
         <div class="row">
             {% if table.add_new_entries %}