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/multithreading/phong.vert

@@ -0,0 +1,49 @@
+// Copyright 2020 Google LLC
+
+struct VSInput
+{
+[[vk::location(0)]] float3 Pos : POSITION0;
+[[vk::location(1)]] float3 Normal : NORMAL0;
+[[vk::location(2)]] float3 Color : COLOR0;
+};
+
+struct PushConsts
+{
+	float4x4 mvp;
+	float3 color;
+};
+[[vk::push_constant]]PushConsts pushConsts;
+
+struct VSOutput
+{
+	float4 Pos : SV_POSITION;
+[[vk::location(0)]] float3 Normal : NORMAL0;
+[[vk::location(1)]] float3 Color : COLOR0;
+[[vk::location(3)]] float3 ViewVec : TEXCOORD1;
+[[vk::location(4)]] float3 LightVec : TEXCOORD2;
+};
+
+VSOutput main(VSInput input)
+{
+	VSOutput output = (VSOutput)0;
+	output.Normal = input.Normal;
+
+	if ( (input.Color.r == 1.0) && (input.Color.g == 0.0) && (input.Color.b == 0.0))
+	{
+		output.Color = pushConsts.color;
+	}
+	else
+	{
+		output.Color = input.Color;
+	}
+
+	output.Pos = mul(pushConsts.mvp, float4(input.Pos.xyz, 1.0));
+
+    float4 pos = mul(pushConsts.mvp, float4(input.Pos, 1.0));
+    output.Normal = mul((float3x3)pushConsts.mvp, input.Normal);
+//	float3 lPos = ubo.lightPos.xyz;
+float3 lPos = float3(0.0, 0.0, 0.0);
+    output.LightVec = lPos - pos.xyz;
+    output.ViewVec = -pos.xyz;
+	return output;
+}