Fix Light rendering (#188)

Change the Light rendering such that the light position is given in eye space as is the common practice.
Previous implementation had light position given in model space which makes it extra hard to render a few models in the same world
with some fixed lighting.

assets/shader/util.vert

@@ -238,9 +238,9 @@ void render(vec3 vertex, vec3 normal, mat4 viewmodel, mat4 projection, vec3 ligh
 {
     vec4 position_camspace = viewmodel * vec4(vertex,  1);
     // normal in world space
-    o_normal               = normal;
+    o_normal               = vec3(transpose(inverse(viewmodel)) * vec4(normal,0));
     // direction to light
-    o_lightdir             = normalize(light[3] - vertex);
+    o_lightdir             = normalize(light[3] - vec3(position_camspace));
     // direction to camera
     o_vertex               = -position_camspace.xyz;
     // screen space coordinates of the vertex