ui: add paginator to top of problem_main page

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

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