ui: fix assign text & core: allow owner get homework detail (#345)

packages/ui-default/templates/contest_edit.html

@@ -70,6 +70,7 @@
               columns:4,
               label:'Assign',
               name:'assign',
+              placeholder:_('Group / UID'),
               value:tdoc.assign|default(''),
               row:false
             }) }}

packages/ui-default/templates/homework_edit.html

@@ -66,6 +66,7 @@
                 columns:4,
                 label:'Assign',
                 name:'assign',
+                placeholder:_('Group / UID'),
                 value:tdoc.assign|default('')
             }) }}
           </div>

packages/ui-default/templates/problem_edit.html

@@ -43,7 +43,7 @@
                row:false,
                columns:3,
                label:'Assign',
-               help_text:'Assigned groups',
+               placeholder:_('Group / UID'),
                name:'assign',
                value:pdoc.assign|default([])|join(', ')
              }) }}