contextlinker: delete co
when a co is deleted the context links should be deleted too.
this can only be implemented once contextlinker is moved to the core.
what to do when it forms a bridge between 2 other co's?
B is alternative of A
C is alternative of B
through B, A is linked to C
when B is deleted, the 2 links should obviously be deleted too BUT maybe they should be replace with a link between A and C?