Elemrnt rotations

[swhite2401]

This PR is a follow-up of #512. It was pointed out that there was no function to provide pitch and yaw in python. The proposed solution was using the wrong coordinate system and needed to be improved.

The change of coordinate from angle (input argument) to momentum is done using the R1 and R2 matrices.

relative option is still available but a bit tricky because some of the transformations are not commutative.
This implementation is a at the stage of a proposal, ideas and suggestions welcome!

If we are happy with this, it can easily be ported to matlab.

[swhite2401]

@elafmusa, I could not add you as reviewer but could you please check this is doing what you expected? Thanks!

[lfarv]

@swhite2401 : Just for my understanding: why is it necessary to round the rotation values?

[swhite2401]

@swhite2401 : Just for my understanding: why is it necessary to round the rotation values?

I had rounding errors of ~1e-19 when applying a transformation and then reverting if with -angle and was not getting exactly identity and zero translation.... I got annoyed by this so I am rounding the angles.
I suppose this comes from the calculation of the previous angles a shift.

It is not necessary, more of a cosmetic measure

[simoneliuzzo]

I think this is a nice addition. I do not have time to review, so I removed myself from reviewers.

[elafmusa]

@swhite2401 I tested the implemented functions, and it works as expected thanks!

[swhite2401]

@swhite2401 I tested the implemented functions, and it works as expected thanks!

Ok I merge, you may switch back to the master branch