Changing ID card skins at the HoPs computer

* you can change an ID card icon_state using the HoP computer.

you can only change it anytime you can change access levels, so basically, only people with valid credentials can change the skin.

![ ] (http://i.imgur.com/mljSEAu.png)

If you don't want people to have access to a certain card skin, such as centcom_old, or syndie, it's as simple as commenting it ou in the ``card_skins`` list (card.dm line 13)
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