all: generate json, not code

This includes modifying horsebot to use the generated JSON, as well as
moving the generator to another cmd/ directory.

Remove the generated code while we're here.
Koka tests still have to be updated, but it requires a JSON parser.

cmd/horsegen/sql/skill-group.sql

@@ -0,0 +1,15 @@
+WITH skill_groups AS (
+	SELECT DISTINCT group_id FROM skill_data
+)
+SELECT
+	g.group_id,
+	IFNULL(s1.id, 0) AS skill1,
+	IFNULL(s2.id, 0) AS skill2,
+	IFNULL(s3.id, 0) AS skill3,
+	IFNULL(m1.id, 0) AS skill_bad
+FROM skill_groups g
+	LEFT JOIN skill_data s1 ON g.group_id = s1.group_id AND s1.group_rate = 1
+	LEFT JOIN skill_data s2 ON g.group_id = s2.group_id AND s2.group_rate = 2
+	LEFT JOIN skill_data s3 ON g.group_id = s3.group_id AND s3.group_rate = 3
+	LEFT JOIN skill_data m1 ON g.group_id = m1.group_id AND m1.group_rate = -1
+ORDER BY g.group_id