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/shadowmapping/scene.frag

@@ -0,0 +1,66 @@
+#version 450
+
+layout (binding = 1) uniform sampler2D shadowMap;
+
+layout (location = 0) in vec3 inNormal;
+layout (location = 1) in vec3 inColor;
+layout (location = 2) in vec3 inViewVec;
+layout (location = 3) in vec3 inLightVec;
+layout (location = 4) in vec4 inShadowCoord;
+
+layout (constant_id = 0) const int enablePCF = 0;
+
+layout (location = 0) out vec4 outFragColor;
+
+#define ambient 0.1
+
+float textureProj(vec4 shadowCoord, vec2 off)
+{
+	float shadow = 1.0;
+	if ( shadowCoord.z > -1.0 && shadowCoord.z < 1.0 ) 
+	{
+		float dist = texture( shadowMap, shadowCoord.st + off ).r;
+		if ( shadowCoord.w > 0.0 && dist < shadowCoord.z ) 
+		{
+			shadow = ambient;
+		}
+	}
+	return shadow;
+}
+
+float filterPCF(vec4 sc)
+{
+	ivec2 texDim = textureSize(shadowMap, 0);
+	float scale = 1.5;
+	float dx = scale * 1.0 / float(texDim.x);
+	float dy = scale * 1.0 / float(texDim.y);
+
+	float shadowFactor = 0.0;
+	int count = 0;
+	int range = 1;
+	
+	for (int x = -range; x <= range; x++)
+	{
+		for (int y = -range; y <= range; y++)
+		{
+			shadowFactor += textureProj(sc, vec2(dx*x, dy*y));
+			count++;
+		}
+	
+	}
+	return shadowFactor / count;
+}
+
+void main() 
+{	
+	float shadow = (enablePCF == 1) ? filterPCF(inShadowCoord / inShadowCoord.w) : textureProj(inShadowCoord / inShadowCoord.w, vec2(0.0));
+
+	vec3 N = normalize(inNormal);
+	vec3 L = normalize(inLightVec);
+	vec3 V = normalize(inViewVec);
+	vec3 R = normalize(-reflect(L, N));
+	vec3 diffuse = max(dot(N, L), ambient) * inColor;
+
+	outFragColor = vec4(diffuse * shadow, 1.0);
+
+}