remove old version of common.php
add inlink to session
show overview table of tables
new: canonicalize_joins(): more flexible handling of JOINS
     allow joins in sql_delete();
new: sql_handle_delete_action(): generic handler for actions 'try', 'count', 'check', 'abort'
     in sql_delete_*()-functions
show authentication methods in peoplelist
disable positions-database (under construction)
remove outdated doc line
dangling links handling: move to anylist (wip)