3D radial trajectory bundle

[Daval-G]

This PR adds four 3D radial trajectories from the literature mentioned in issue #106:

1. initialize_3D_phyllotaxis_radial from "Spiral Phyllotaxis: The Natural Way to Construct a 3D Radial Trajectory in MRI" Davide Piccini et al. (2011). Radial shots are oriented following a Fibonacci sphere lattice.
2. initialize_3D_golden_means_radial from "Temporal Stability of Adaptive 3D Radial MRI Using Multidimensional Golden Means", Rachel W. Chan (2009). Radial shots are oriented following Fibonacci-based non-repeating angles.
3. initialize_3D_wong_radial from "A Strategy for Sampling on a Sphere Applied to 3D Selective RF Pulse Design", Sam T. S. Wong and Mark S. Roos (1994). Radial shots are oriented following one or multiple spiral(s) over the k-space sphere.
4. initialize_3D_park_radial from "A radial sampling strategy for uniform k-space coverage with retrospective respiratory gating in 3D ultrashort-echo-time lung imaging", Jinil Park et al. (2016). This pattern is based on Wong et al. (1994) from initialize_3D_wong_radial, enforcing a single spiral and ordering shots in a different way.

Documentation & examples coming soon.
The illustration below shows the tips of each radial shot for each of the four patterns.

[Daval-G]

For some reason this PR got entangled with PR #105. It should be alright

[philouc]

Thanks @Daval-G for this awesome work. I question came to my MIND. Should we use this new 3D radial traj available in MRI-NUFFT as initialization for 3D SPARKLING in the future? Do you expect any improvement notably for fMRI?

[paquiteau]

Awesome work once again!

Could you resubmit with only c98d54a ? I think that the only
one you want in the branch.

[chaithyagr]

I have also come across AZETK: https://pubmed.ncbi.nlm.nih.gov/32936490/
The advantage of this is that we can group a bunch of shots present spatially close in time and expect nearly good "uniform coverage still", sorta similar to 3) and 4).
@philouc when it comes to shot order atleast, I feel these methods are way better than what we used to do. I plan to take these methods in as good SPARKLING initalizers eventually

[chaithyagr]

Coming to the examples, maybe we come up with "Trajectories" gallery which is more automatized? This could be a subject of another PR , which brings get_trajectory in place. WDYT @paquiteau

[philouc]

Thanks @chaithyagr ; SHould we put that in the Maxime's plate for fMRI?

[chaithyagr]

I think with the help of SHFJ (its a work from their team) we could see if we can get their implementations up. This could be a good oppurtunity for them to showcase their work and also foster better collaboration!

[Daval-G]

This PR can be closed, as a cleaner version is available in PR #115.