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/scenario.sql

@@ -0,0 +1,17 @@
+WITH scenario_name AS (
+	SELECT "index" AS id, "text" AS name
+	FROM text_data
+	WHERE category = 237
+), scenario_title AS (
+	SELECT "index" AS id, "text" AS title
+	FROM text_data
+	WHERE category = 119
+)
+SELECT
+	sc.id,
+	n.name,
+	t.title
+FROM single_mode_scenario sc
+	JOIN scenario_name n ON sc.id = n.id
+	JOIN scenario_title t ON sc.id = t.id
+ORDER BY sc.id