Following the discussion, I made the following changes: - there is now code to create a Rotation3D from ZYZ euler angles (moved from the old Euler ange class). Javi needs to fill out the documentation of this method to make it as well specified as the other Euler angle methods (ie are the axis fixed or not) as I don't know the answers to all the necessary questions and they weren't previously documented
- the project.h code uses Rotation3D - Rotation3D caches the rotation matrix since it made rotations about 20% faster and memory seemed unlikely to be an issue. There is a benchmark for this. - the 2D rotation class is now Rotation2D
- all tests still pass