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/computeparticles/particle.vert

@@ -0,0 +1,21 @@
+#version 450
+
+layout (location = 0) in vec2 inPos;
+layout (location = 1) in vec4 inGradientPos;
+
+layout (location = 0) out vec4 outColor;
+layout (location = 1) out float outGradientPos;
+
+out gl_PerVertex
+{
+	vec4 gl_Position;
+	float gl_PointSize;
+};
+
+void main () 
+{
+  gl_PointSize = 8.0;
+  outColor = vec4(0.035);
+  outGradientPos = inGradientPos.x;
+  gl_Position = vec4(inPos.xy, 1.0, 1.0);
+}