fix three missed conversions to closures.  switch to extending math prototypes rather than replacing them.  This is to ensure that types created in closures within a type's prototype definition get their prototype updated with the full definition.

Renamed Vector3 projectPoint() to applyProjection() as per @WestLangley suggestion in bb873d16.

Changed back some .projectPoint() to .applyMatrix4() as per bb873d16.

Renamed ShaderLib's 'normal2' shader to 'normalmap' as suggested in 4276c9f5.

@WestLangley I've changed most of the vector.applyMatrix4() to vector.projectPoint().
Feel free to change back the ones that aren't needed (or let me know which ones can need to be changed back and I will do it).

ShaderUtils relied on ShaderChunks so this created troubles when trying to use three-canvas and three-extras. Besides, better to keep a single library of shaders.

This is the bug I started the day with. And I kept finding other issues on the way. I think it's now fixed, but this made me realise how convoluted this exporter is :(

Blender Exporter: I don't think parsing the groups is needed. It exports the objects twice (or more) otherwise.

This is a formatting commit, it removes an unnecessary else branch.

The functionality removed is repeated directly after this code block.
The entire process is actually being done twice, which is undoubtedly incorrect or otherwise very unclear.

Given that it is simply doing 3 actions:

a) Adjusting the pitch/yaw based on the mouse position deltas, then multiplying that by the lookSpeed.
b) Clamping, transforming the pitch space (to the X,Z coordinate frame) and then converting the pitch/yaw (lat/lon) to radians.
c) Calculating the target position 100 units in the direction specified by the pitch/yaw.

This process has no reason to be repeated.

Plane: Removed normalize() from setFromNormalAndCoplanarPoint and added it back to setFromCoplanarPoints. As suggested in 5c6b5746.