Add ability for Modular Arena Gameboards

[sIKE23]

@ACG8 My thoughts here, are to add a button on the Arena list (at the bottom) that would trigger a button list of Arena maps.

Two folders would be created under maps, arena and domination, and the all of the maps would be placed in the proper folder. The arena.py would point to the maps/arena folder and domination.py would point to the maps/domination folder. If we need to add future modular map support for another expansion we would do the same it expansion.py points to maps/expansion.

Thoughts?

[ACG8]

Sure, that seems like a good structure to me.