Activity: fixes in voter

* the role CREATE is now transformed to CREATE_ACCOMPANYING_COURSE or
CREATE_PERSON when the subject is, respectively, a course or a person;
* the button at the list of activities is now labeled "create"
* the role FULL give access to both role
acTIVITY_CREATE_ACCOMPANYING_COURSE and ACTIVITY_CREATE_PERSON, but not
ACTIVITY_CREATE directly.

src/Bundle/ChillActivityBundle/Resources/views/Activity/listAccompanyingCourse.html.twig

@@ -24,7 +24,7 @@
     <ul class="record_actions sticky-form-buttons">
         <li>
             <a href="{{ path('chill_activity_activity_new', {'person_id': person_id, 'accompanying_period_id': accompanying_course_id}) }}" class="btn btn-create">
-                {{ 'Add a new activity' | trans }}
+                {{ 'Create'|trans }}
             </a>
         </li>
     </ul>