Re-implement %DECKNAME% and Style setting through Global Attributes

[bloodwurm]

With the implementation of Global Attributes, should be able to change the implementation of %DECKNAME% to a fully fledged Global Attribute.

Also, the DeckPanelEditor builds and displays a Style combo box so that the user can switch between possible styles. Would be great to also implement Style through Global Attributes, unifying all those "global" parameters.

[bloodwurm]

I've looked into changing DECKNAME into a Global attribute but I'm unsure it's a good thing. A deck would anyways need a name, so we can consider it being part of a Deck's definition, no need to make it an attribute.