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/inputattachments/attachmentread.frag

@@ -0,0 +1,33 @@
+#version 450
+
+layout (input_attachment_index = 0, binding = 0) uniform subpassInput inputColor;
+layout (input_attachment_index = 1, binding = 1) uniform subpassInput inputDepth;
+
+layout (binding = 2) uniform UBO {
+	vec2 brightnessContrast;
+	vec2 range;
+	int attachmentIndex;
+} ubo;
+
+layout (location = 0) out vec4 outColor;
+
+vec3 brightnessContrast(vec3 color, float brightness, float contrast) {
+	return (color - 0.5) * contrast + 0.5 + brightness;
+}
+
+void main() 
+{
+	// Apply brightness and contrast filer to color input
+	if (ubo.attachmentIndex == 0) {
+		// Read color from previous color input attachment
+		vec3 color = subpassLoad(inputColor).rgb;
+		outColor.rgb = brightnessContrast(color, ubo.brightnessContrast[0], ubo.brightnessContrast[1]);
+	}
+
+	// Visualize depth input range
+	if (ubo.attachmentIndex == 1) {
+		// Read depth from previous depth input attachment
+		float depth = subpassLoad(inputDepth).r;
+		outColor.rgb = vec3((depth - ubo.range[0]) * 1.0 / (ubo.range[1] - ubo.range[0]));
+	}
+}