- Replaced BattleSide namespace-enum with enum class
- Merged two different BattleSide enum's into one
- Merged BattlePerspective enum into BattleSide enum
- Changed all places that use integers to represent battle side to use
BattleSide enum
- Added BattleSideArray convenience wrapper for std::array that is
always 2-elements in size and allows access to its elements using
BattleSide enum
