Add getter

[ManuelBoesl]

Currently we use the properties directly in many cases, which could change the property even though we don't want to. To prevent this, we need getters (and setters).
E.g. change help_list = computer.cards to help_list = computer.get_cards().
Now we have a copy and not the cards directly.
Hopefully this fixes some strange problems i ran into during making the game_logic