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/inputattachments/attachmentwrite.frag

@@ -0,0 +1,24 @@
+// Copyright 2020 Google LLC
+
+struct VSOutput
+{
+[[vk::location(0)]] float3 Color : COLOR0;
+[[vk::location(1)]] float3 Normal : NORMAL0;
+[[vk::location(2)]] float3 ViewVec : TEXCOORD1;
+[[vk::location(3)]] float3 LightVec : TEXCOORD2;
+};
+
+float4 main(VSOutput input) : SV_TARGET
+{
+	// Toon shading color attachment output
+	float intensity = dot(normalize(input.Normal), normalize(input.LightVec));
+	float shade = 1.0;
+	shade = intensity < 0.5 ? 0.75 : shade;
+	shade = intensity < 0.35 ? 0.6 : shade;
+	shade = intensity < 0.25 ? 0.5 : shade;
+	shade = intensity < 0.1 ? 0.25 : shade;
+
+	return float4(input.Color * 3.0 * shade, 1);
+
+	// Depth attachment does not need to be explicitly written
+}