Editor: Added @drewnoakes dragover handling. Seesms like droping wasn't working on some setups. See #3035.

Removed Vector* add() to addVectors() and addSelf() to add(). Same with sub, cross, min, max, lerp... Renamed Matrix* and Quaternion multiply() to multiplyMatrices(), multiplyQuaternions() and multiplySelf() to multiply(). See #2860.
Good thing we have a ton of examples to make sure nothing is broken. The unit tests also helped. However, I suspect I've left something unchanged.

I think it's a bit redundant.

Also moved some more ui.js styles to the app's css.

This gave me a hard time in a presentation where I was embeding the editor in one of the slides and it was stealing the focus...

It's too much work to remove everything to get a useful state.
Maybe we can add the current "test" scene loadable somewhere in the menu?

This got broken after GeometryLoader got removed, using instead JSONLoader.

This way the panel illustrates the API better.
It's not too intuitive but eventually the (future) helper will probably make it uneeded.

Ok, lets go with blue.

Still not happy about it, need more time to see what the right style for all this is.

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).

Also nicer whitespace formatting for lights and cameras in strings generated by SceneExporter.

I kinda got used to this behaviour from the htmleditor.