I think the way the recursive procrustes is implemented might have a bug, but I need your opinion. The result of `GeneralizedProcrustesAnalysis` has two things among others: `gpa.target` and `gpa.mean_aligned_shape`. They are both `PointCloud` instances. If the user doesn't provide a target shape, then these two are equal as expected. 
However, if the user provides a target shape, they will still be both equal (to the mean shape). I would expect `gpa.mean_aligned_shape` to have the mean shape and `gpa.target` to store the shape provided by the user. What do you think guys? Should we change this?