[Gameplay] - Let Spartans start with a Champion.

The Kushites start their games with an healer, the Mauryas with an
elephant. The Spartans were known for their superior hoplites; this
patch gives them one champion infantry at game start, to make them feel
a bit different from other factions. It won't suddenly make them win
games, although it could help a bit defending against very early raids.
Somewhat relevant forum threads:
https://wildfiregames.com/forum/topic/35419-differentiating-civs-spartans/
and
https://wildfiregames.com/forum/topic/22868-rethinking-the-meta-with-sparta-a-historical-approach/?tab=comments#comment-338125.

Patch by: @Nescio
Differential revision: D3412
Reviewed by: @Palaxin, @wraitii
Reservations by: @ValihrAnt
Comment by: @borg-
This was SVN commit r24693.

binaries/data/mods/public/simulation/data/civs/spart.json

@@ -45,6 +45,9 @@
 		},
 		{
 			"Template": "units/spart/cavalry_javelineer_b"
+		},
+		{
+			"Template": "units/spart/champion_infantry_spear"
 		}
 	],
 	"Formations": [
@@ -75,6 +78,7 @@
 		"Agesipolis"
 	],
 	"SkirmishReplacements": {
+		"skirmish/units/special_starting_unit": "units/spart/champion_infantry_spear",
 		"skirmish/structures/default_house_10": "structures/{civ}/house",
 		"skirmish/structures/default_wall_tower": "",
 		"skirmish/structures/default_wall_gate": "",