Decomposing query -> data vectors

[cavemanloverboy]

In several applications which require evaluation of isotropy, such as cosmology, one needs not only the distances to queries but the full K-dimensional vector pointing from the query to the data point (or some projections of this vector). For simulation boxes, these projections are axis-aligned. For other applications like lightcone simulations or halo/galaxy catalogs in spherical coordinates, the directions of projection (i.e. line-of-sight and transverse) are not axis-aligned.

I'd like to add these types of queries. They can be gated behind #[cfg(feature = "cosmology")] to not interfere with the rest of the codebase.