Make clear all permissions translatable

Make "Clear all permissions" translatable in `main/templates/user/user_list`
Where possible prefer to break it like this.. unless is very long line in HTML

```
<a href="{{update_query_argument('permissions', ignore='cursor')}}" class="btn btn-default" title="{{_('Clear all permissions')}}">
  <i class="fa fa-times"></i>
</a>
```