List view: dropped call to stopListening. Done in base "remove" call

Backbone's remove function already calls "stopListening", no need to
call it once again in derived classes.
CardPanel: fixed "addChild" not to call setChildren

Calling setChildren effectively removes former children views, meaning
that the "remove" method of these views gets called. But "addChild"
appends a child to a list of children that have already been set, so
it must not call "setChildren".