debug(): fix handling of debug requests; logger(): allow to disable ordinary logging
new page: "studiengaenge"
split persistentvars, tests from maintenance.php into separate scripts
fix persistentvars_view; add new maintenance inlinks
make anylist application-aware (for tables that support it)
garbage collection handling: new functions sql_prune_transactions(), prune_persistentvars()
improve maintenance.php
rename: handle_action() -> handle_actions(); store handles actions in global variable; adapt all calls