Introduce Sides

[greenstack]

Though the concept of Sides was removed in 0.2.0-alpha, there is another way in which they can be useful. Sides can be considered a group of allied teams.

Potential benefits of introducing sides:

• Sides aren't directly controlled by a player or AI while a Team is.
• Sides can simplify teams finding allied, opposing, or neutral teams - if a team has a reference to its Side, it can just grab the teams contained by that side.
• Victory can be determined on a side-by-side basis over a team-by-team basis (though we may want to preserve this functionality).

I don't see Sides as an 0.2.0-alpha feature, but rather as a 0.3.0-alpha. This is up for discussion, however.

[greenstack]

I've been thinking about this recently, and I think a better way to do this would be with an alliance graph type. The alliance graph would allow developers to define alliances by treating teams as nodes and their relationship as edges. I think this would also be more dynamic, as changes to alliances could happen as a part of an action or reaction during battle; while Sides could potentially handle this, I think the alliance graph makes more sense in the long run.