Order hostgroups in users filter alphabetically

The list of hostgroups in /user/edit, filters tab, is ordered by creation date. It's annoying to search for a certain hostgroup, so now they're ordered alphabetically. Nested hostgroups are taken into account, so that "/base/nested" goes before "/base/zorg".

In the future, maybe a search box would be very apt for this job. It's slightly annoying with ~300 hostgroups.