Improve searching in member list (convert from using JavaScript to using URL parameters)

[ddabble]

[Originally created on the "Dev-Web" Trello board, by @ddabble on April 6, 2022]

It's currently not possible to search any other fields than the ones that appear in the list. This should be fixed by converting the entire list to not use JavaScript for searching/filtering/sorting, but instead use URL parameters that are parsed by Django using e.g. a form, and then simply use queryset methods for searching/filtering/sorting - just like on the Django admin site.