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/depthpass.frag

@@ -0,0 +1,13 @@
+#version 450
+
+layout (set = 1, binding = 0) uniform sampler2D colorMap;
+
+layout (location = 0) in vec2 inUV;
+
+void main() 
+{	
+	float alpha = texture(colorMap, inUV).a;
+	if (alpha < 0.5) {
+		discard;
+	}
+}