Euler could be a first class object like Matrix44 and Vector3

[klattimer]

I was trying to use this library, and importing Euler in the same way as Quaternions or Vectors seems not done. This also appears to apply to line, plane and others.

[adamlwgriffiths]

The geometric tests library was a late addition and honestly should be put into an experimental module as it is not up to snuff.
Adding a class for Euler seems reasonable.