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.frag

@@ -0,0 +1,15 @@
+#version 450
+
+layout (binding = 0) uniform sampler2D samplerColorMap;
+layout (binding = 1) uniform sampler2D samplerGradientRamp;
+
+layout (location = 0) in vec4 inColor;
+layout (location = 1) in float inGradientPos;
+
+layout (location = 0) out vec4 outFragColor;
+
+void main () 
+{
+	vec3 color = texture(samplerGradientRamp, vec2(inGradientPos, 0.0)).rgb;
+	outFragColor.rgb = texture(samplerColorMap, gl_PointCoord).rgb * color;
+}