Refactor gameplay menus into owned scenes

buildings/GasBurnerBuildingDefinition.tres

@@ -9,6 +9,7 @@ script = ExtResource("3")
 input_buffers = {
 "gas": 40
 }
+collected_outputs = PackedStringArray("energy")
 conversion_input = "gas"
 conversion_output = "energy"
 conversion_rate = 1.0
@@ -27,6 +28,7 @@ build_resource_costs = {
 action_icon = 33
 menu_icon = 33
 visual_scene = ExtResource("2")
+capabilities = PackedStringArray("gas_burner")
 logistics = SubResource("Resource_logistics")
 map_color = Color(0.95, 0.35, 0.15, 1)
 map_sides = 5