Testing the impact of normalization of transformed normals in vertex shaders (phong, normal, normalmap, skin simple).

It seems the effects on performance are minimal: in several random examples it's either not measurable, or just a tiny bit worse.

See #2613
Editor: plugged object delete and scene reset actions into menubar.

Default scene on the initialization is now created via resetScene action, in the same way like via menubar.
Editor: added warning when trying to export geometry for objects without geometry (lights, cameras, etc).
Removed Vector*.isZero()
Removed Vector*.isZero()
Editor: added mouseover styling for menubar items.
Editor: added slight borders around Viewport.

This is to make it look better when Viewport clear color is close to UI chrome colors.
Editor: plugged in adding of sphere / cube / plane to menubar.

For the moment using just fixed predefined tessellations. I wonder what UI would be good for choosing this.

Todo: better naming scheme for newly created objects.
Editor: added handling of removal of lights from the scene.
Editor: plugged in adding of point and directional lights to menubar.
Merge remote-tracking branch 'alteredq/dev' into dev
Editor: Cleaned up menubar.
Editor: More menubar clean up.
Editor: Changed shortcut for hiding helpers to "Esc".
I kinda got used to this behaviour from the htmleditor.
Editor: Fixed CSS indentation.
Updated scene format to use singular "material" property instead of "materials" array for meshes.

Bumped scene format version to 3.2

Modified correspondingly SceneLoader, SceneExporter, Blender scene exporter and example scene files.

See #2628
Added handling of MeshFaceMaterial.materials to scene format / SceneLoader.

See #2628 and #2623
Editor: plugged in adding of SpotLight, HemisphereLight and AmbientLight to menubar.

Also nicer whitespace formatting for lights and cameras in strings generated by SceneExporter.
Editor: simplified object removal.
Editor: deallocating removed objects and helpers.

I wonder what to do about geometries and materials used by removed objects. Seems like we would need to implement some reference counting scheme (we can't just remove deleted object subcomponents as they could be shared).