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/particlefire/particle.frag

@@ -0,0 +1,52 @@
+// Copyright 2020 Google LLC
+
+Texture2D textureSmoke : register(t1);
+SamplerState samplerSmoke : register(s1);
+Texture2D textureFire : register(t2);
+SamplerState samplerFire : register(s2);
+
+struct VSOutput
+{
+	float4 Pos : SV_POSITION;
+[[vk::location(0)]] float4 Color : COLOR0;
+[[vk::location(1)]] float Alpha : TEXCOODR0;
+[[vk::location(2)]] int Type : TEXCOODR1;
+[[vk::location(3)]] float Rotation : TEXCOODR2;
+[[vk::location(4)]] float2 CenterPos : POSITION1;
+[[vk::location(5)]] float PointSize : TEXCOORD3;
+};
+
+float4 main (VSOutput input) : SV_TARGET
+{
+	float4 color;
+	float alpha = (input.Alpha <= 1.0) ? input.Alpha : 2.0 - input.Alpha;
+
+	// Rotate texture coordinates
+	// Rotate UV
+	float rotCenter = 0.5;
+	float rotCos = cos(input.Rotation);
+	float rotSin = sin(input.Rotation);
+
+	float2 PointCoord = (input.Pos.xy - input.CenterPos.xy) / input.PointSize + 0.5;
+
+	float2 rotUV = float2(
+		rotCos * (PointCoord.x - rotCenter) + rotSin * (PointCoord.y - rotCenter) + rotCenter,
+		rotCos * (PointCoord.y - rotCenter) - rotSin * (PointCoord.x - rotCenter) + rotCenter);
+
+	float4 outFragColor;
+	if (input.Type == 0)
+	{
+		// Flame
+		color = textureFire.Sample(samplerFire, rotUV);
+		outFragColor.a = 0.0;
+	}
+	else
+	{
+		// Smoke
+		color = textureSmoke.Sample(samplerSmoke, rotUV);
+		outFragColor.a = color.a * alpha;
+	}
+
+	outFragColor.rgb = color.rgb * input.Color.rgb * alpha;
+	return outFragColor;
+}