MLP should do the actual JSON check

[tremblap]

Todo was place-holder :)

flucoma-core/include/data/FluidJSON.hpp

Lines 406 to 412 in ab9c650

	//TODO
	bool check_json(const nlohmann::json &j, const MLP &) {
	return fluid::check_json(j,
	{"layers"},
	{JSONTypes::ARRAY}
	);
	}

[tremblap]

https://discourse.flucoma.org/t/fluid-mlpregressor-not-returning-prediction-inside-collapsed-m4l-device/2259/9

[tremblap]

https://discourse.flucoma.org/t/fluid-mlpregressor-not-returning-prediction-inside-collapsed-m4l-device/2259/9