Rework GlobeControls

[nosy-b]

The GlobeControls class has evolved a lot since the creation of itowns2. It is of great help but it is getting very messy with 2000 lines of delicious spaghetti.

A complete refactorization is necessary.

[autra]

Yes!

A basic idea: the new GlobeControls should be a FrameRequester. We use the event listeners to only set states (panning, zooming, etc...) and relevant variables (mouseDown positions and stuff). We do the heavy work in the update function of this GlobeControls. See other controls for inspiration.

It might be necessary to add other anchors for FrameRequester in MainLoop (being called before rendering, after rendering, before update, after update etc...) to be able to do everything we want (without having to setup timeout, promises on command-empty, or dummy frame requesters).

Last but not least, I think we can work incrementally by having a GlobeControls2.js, and replacing the former GlobeControls once we reach feature parity, instead of trying to rewrite everything in one PR.

[gchoqueux]

Since #795, Globe Controls has been greatly refactoring and debugging.
It still remains

• FrameRequester
• Collision refacto