Cytocipher optimised

Bug fixes and speed optimisations, namely Numba and smarter datastructure usage at bottle-necks.

Cytocipher MNN

Added pip installation, and also flexible MNN determination by letting the user run sc.tl.neighbors first, and then using this to determine the cluster-level MNNs.

Cytocipher Bioarchived v2

Added updating p-value cutoffs without needed to re-calculate many key statistics.
Added extra diagnostic plots (sankey diagram, volcano plot, bias checks).

Cytocipher bioarchived

Initial version used to produce results in the bioarchived paper.