core&ui&elastic: support elastic search and allow search result pagination

packages/ui-default/templates/partials/problem_list.html

@@ -6,7 +6,7 @@
 {% if not pdocs.length %}
   {{ nothing.render('Sorry, there is no problem in the problem set') }}
 {% else %}
-  {{ paginator.render(page, ppcount, position='top') }}
+  {{ paginator.render(page, ppcount, position='top', add_qs=qs) }}
   <table class="data-table hide-problem-tag">
     <colgroup>
       <col class="col--checkbox display-mode-hide">
@@ -73,6 +73,6 @@
     {%- endfor -%}
     </tbody>
   </table>
-  {{ paginator.render(page, ppcount) }}
+  {{ paginator.render(page, ppcount, add_qs=qs) }}
 {% endif %}
 </div>

packages/ui-default/templates/partials/problem_stat.html

@@ -1,3 +1,3 @@
 <div data-fragment-id="problem_stat">
-  <p>{{ _('{0} problems').format(pcount) }}</p>
+  <p>{{ _('{0} problems' if pcountRelation == 'eq' else 'Over {0} problems').format(pcount) }}</p>
 </div>