Add card type category

[mmougy]

In order to know if a card is a player card or an encounter card
adding a category of type might be helpful

It implements the definition from Rules Reference 1.6:

[jordanweiler]

Don't we already mark the card's faction_code as encounter? Is this duplicating something we already can figure out?

[Kamalisk]

I guess this is useful if you wanted to filter by those types without loading card data, but yes the data is already in the card data.