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/pbrtexture/skybox.frag

@@ -1,39 +0,0 @@
-#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);
-}