Added capability to merge organisations

- Added an interface for organisation
- Added beforeDelete and beforeMerge callbacks
- Added hard/soft delete to organisations

templates/tables/organisations.html.twig

@@ -70,6 +70,11 @@
                         <i class="fas fa-edit"></i> {% endverbatim %}{{translate("ORGANISATION.EDIT")}}{% verbatim %}
                         </a>
                     </li>
+                    <li>
+                        <a href="#" data-slug="{{row.slug}}" class="js-organisation-merge">
+                        <i class="fas fa-object-group"></i> {% endverbatim %}{{translate("ORGANISATION.MERGE")}}{% verbatim %}
+                        </a>
+                    </li>
                     <li>
                         <a href="#" data-slug="{{row.slug}}" class="js-organisation-delete">
                         <i class="fas fa-trash-alt"></i> {% endverbatim %}{{translate("ORGANISATION.DELETE")}}{% verbatim %}