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/shadowmappingcascade/debugshadowmap.frag

@@ -0,0 +1,14 @@
+#version 450
+
+layout (binding = 1) uniform sampler2DArray shadowMap;
+
+layout (location = 0) in vec2 inUV;
+layout (location = 1) flat in uint inCascadeIndex;
+
+layout (location = 0) out vec4 outFragColor;
+
+void main() 
+{
+	float depth = texture(shadowMap, vec3(inUV, float(inCascadeIndex))).r;
+	outFragColor = vec4(vec3((depth)), 1.0);
+}