list view: Allow for reacting to release events

[peter-ha]

QskAbstractButton will emit clicked() (and released()) upon a keyReleaseEvent(). Also QListView / QAbstractItemView has a signal pressed() and clicked().

So in the same way we need a signal in QskListView that lets the user react on a release() event, like e.g. clicked( int row ) or released( int row ) or similar.