handle non-stack "$stack" entries
fix handling of empty selection with uid_choices
support debugging in sql_query()
fix dropdown selector in string_element()
fix download button
public page structure: list professors under research
optimize alink_{person|group_view(): cache entries
implement more columns in group: status, professor_groups_id, keyarea
pp/views.php: optimize peoplelist_view(): do not query affiliations for each row