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/glsl/pbrtexture/skybox.frag

@@ -0,0 +1,39 @@
+#version 450
+
+layout (binding = 2) uniform samplerCube samplerEnv;
+
+layout (location = 0) in vec3 inUVW;
+
+layout (location = 0) out vec4 outColor;
+
+layout (binding = 1) uniform UBOParams {
+	vec4 lights[4];
+	float exposure;
+	float gamma;
+} uboParams;
+
+// From http://filmicworlds.com/blog/filmic-tonemapping-operators/
+vec3 Uncharted2Tonemap(vec3 color)
+{
+	float A = 0.15;
+	float B = 0.50;
+	float C = 0.10;
+	float D = 0.20;
+	float E = 0.02;
+	float F = 0.30;
+	float W = 11.2;
+	return ((color*(A*color+C*B)+D*E)/(color*(A*color+B)+D*F))-E/F;
+}
+
+void main() 
+{
+	vec3 color = texture(samplerEnv, inUVW).rgb;
+
+	// Tone mapping
+	color = Uncharted2Tonemap(color * uboParams.exposure);
+	color = color * (1.0f / Uncharted2Tonemap(vec3(11.2f)));	
+	// Gamma correction
+	color = pow(color, vec3(1.0f / uboParams.gamma));
+	
+	outColor = vec4(color, 1.0);
+}