also, this renames DeckItem::setInDeck() to DeckItem::wasSetInDeck()
because the former method can easily be confused with a setter method
(which it is not, it is a 'getter').
note that there is a small semantical difference now: the old
signatures specified the status of the whole *item* while the new
variants are specific for a single *data point* of an item. Though at
this point the index passed to the methods is still disregarded..
e6fa1e01a8