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/computeshader/emboss.comp

@@ -1,44 +0,0 @@
-#version 450
-
-layout (local_size_x = 16, local_size_y = 16) in;
-layout (binding = 0, rgba8) uniform readonly image2D inputImage;
-layout (binding = 1, rgba8) uniform image2D resultImage;
-
-float conv(in float[9] kernel, in float[9] data, in float denom, in float offset) 
-{
-   float res = 0.0;
-   for (int i=0; i<9; ++i) 
-   {
-      res += kernel[i] * data[i];
-   }
-   return clamp(res/denom + offset, 0.0, 1.0);
-}
-
-struct ImageData 
-{
-	float avg[9];
-} imageData;	
-
-void main()
-{	
-	// Fetch neighbouring texels
-	int n = -1;
-	for (int i=-1; i<2; ++i) 
-	{   
-		for(int j=-1; j<2; ++j) 
-		{    
-			n++;    
-			vec3 rgb = imageLoad(inputImage, ivec2(gl_GlobalInvocationID.x + i, gl_GlobalInvocationID.y + j)).rgb;
-			imageData.avg[n] = (rgb.r + rgb.g + rgb.b) / 3.0;
-		}
-	}
-
-	float[9] kernel;
-	kernel[0] = -1.0; kernel[1] =  0.0; kernel[2] =  0.0;
-	kernel[3] = 0.0; kernel[4] = -1.0; kernel[5] =  0.0;
-	kernel[6] = 0.0; kernel[7] =  0.0; kernel[8] = 2.0;
-									
-	vec4 res = vec4(vec3(conv(kernel, imageData.avg, 1.0, 0.50)), 1.0);
-
-	imageStore(resultImage, ivec2(gl_GlobalInvocationID.xy), res);
-}