Move shaders into glsl and hlsl directories

Move `data/shaders` to `data/shaders/glsl`
Move `data/hlsl` to `data/shaders/hlsl`

Fix up shader paths in the cpp files to point to the new glsl location.

`data/shaders/hlsl/compile.py` still overwrites the glsl .spv files (for
now).

Issue: #723

data/shaders/hlsl/stencilbuffer/toon.frag

@@ -0,0 +1,32 @@
+// Copyright 2020 Google LLC
+
+Texture2D textureColorMap : register(t1);
+SamplerState samplerColorMap : register(s1);
+
+struct VSOutput
+{
+[[vk::location(0)]] float3 Normal : NORMAL0;
+[[vk::location(1)]] float3 Color : COLOR0;
+[[vk::location(2)]] float3 LightVec : TEXCOORD2;
+};
+
+float4 main(VSOutput input) : SV_TARGET
+{
+	float3 color;
+	float3 N = normalize(input.Normal);
+	float3 L = normalize(input.LightVec);
+	float intensity = dot(N,L);
+	if (intensity > 0.98)
+		color = input.Color * 1.5;
+	else if  (intensity > 0.9)
+		color = input.Color * 1.0;
+	else if (intensity > 0.5)
+		color = input.Color * 0.6;
+	else if (intensity > 0.25)
+		color = input.Color * 0.4;
+	else
+		color = input.Color * 0.2;
+	// Desaturate a bit
+	color = lerp(color, dot(float3(0.2126,0.7152,0.0722), color).xxx, 0.1);
+	return float4(color, 1);
+}