(Seems I keep returning...)

Gonna raise a concern, I've convinced myself this needs to be mostly reverted. See https://code.wildfiregames.com/D4630#196827, rephrased below:

This diff does three things:

• Use the player-entities's Identity component instead of the cmpPlayer to get the civ code and the name < probably a good change, reduces duplication
• Move the historical data from JSON files to XML, making a lot of the code awkward and resulting in the Engine.GetTemplate fiasco < definitely a bad call, IMO. Just load the JSON data and populate the player-entity Identity at game start.
• Made the Civ template XML the 'core truth' of what civ were available < Definitely broken. JSON files were working well, and the civ XMLs are just setting the gameplay element.

I think only point (1) is actually worthwhile, point (2) just leads to awkwardness and makes point (3) necessary when point (3) is IMO a move in the wrong direction altogether.