Add a link between accompanying period and user

It is now allowed to indicates who make/made the accompanying period.

This feature may be hidden by a specific configuration option. Default
to visible.

Resources/views/AccompanyingPeriod/form.html.twig

@@ -39,6 +39,10 @@
 {% if form.closingMotive is defined %}  
     {{ form_row(form.closingMotive, {'label' : 'Closing motive'} ) }}
 {% endif %}
+
+{% if form.user is defined %}
+    {{ form_row(form.user, {'label': 'Accompanying user'}) }}
+{% endif %}
     
 {{ form_row(form.remark, {'label' : 'Remark' } ) }}