phase of S-wall seed (displacement) and phase from SW differential

[plonghi]

When seeding S walls at branch points, the phase of the displacement of a seed should match
well with that of
e^{i (\theta+pi)} / (x_j - x_i)
However, in certain situations the deviation is significant, not sre if because of numerics or a conceptual mistake.
An example is given by the (unexpected) bending of trajectories when running the config file seeding_type_I, choosing the second configuration within that file.
(The deviation of the phase will be displayed in the output by setting logging mode to 'debug')

Added a short note to the 'documentation' folder, explaining how the current seeding is handled for 3 classes of ramification points (more to add, e.g. for E-type degenerate cases), to help scrutinizing the current logic.

[plonghi]

A memo on an additional improvement.
When computing seeds for branch points of higher ramification index, it's important to avoid picking pairs of sheets that corresponds to weights whose difference isn't a root.
As of now, we compute the sheets, and impose some conditions on the pairs of weights, to avoid doing this.
But it should be possible to use directly the algorithm for sheet-weight alignment to figure out if a pair of sheets is suitable for seeding. The key point is that, while the alignment won't give the actual sheet-weight identification in this case (because that would require tracking sheets from the trivialization basepoint), it should nevertheless give one correct possible sheet-weight identification.
This is enough information to drop all un-suitable sheet pairs when seeding.

[plonghi]

Found the cause of this and fixed in the branch results_for_note