Improve admin templates for event admin entities + activity reason (category) entities and remove delete and show actions for coherence

src/Bundle/ChillEventBundle/Resources/views/Role/new.html.twig

@@ -9,7 +9,7 @@
     {{ form_row(form.type) }}
     {{ form_row(form.active) }}
 
-    <ul class="record_actions">
+    <ul class="record_actions sticky-form-buttons">
         <li class="cancel">
             <a href="{{ path('chill_event_admin_role') }}" class="btn btn-cancel">{{ 'Back to the list'|trans }}</a>
         </li>