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/shadowmapping/quad.frag

@@ -0,0 +1,21 @@
+#version 450
+
+layout (binding = 1) uniform sampler2D samplerColor;
+
+layout (location = 0) in vec2 inUV;
+
+layout (location = 0) out vec4 outFragColor;
+
+float LinearizeDepth(float depth)
+{
+  float n = 1.0; // camera z near
+  float f = 128.0; // camera z far
+  float z = depth;
+  return (2.0 * n) / (f + n - z * (f - n));	
+}
+
+void main() 
+{
+	float depth = texture(samplerColor, inUV).r;
+	outFragColor = vec4(vec3(1.0-LinearizeDepth(depth)), 1.0);
+}