[NTR] Add transcriptomically identified molecular layer interneuron subtypes

[dosumis]

This paper, https://www.nature.com/articles/s41586-021-03220-z , characterises the morphology, physiology + functional implications of molecular profile of two MLI subtypes in mice + has some mapping to human.

There is sufficient multi-modal info to add to CL with properties as described in the paper. If we can establish a clean mapping onto WMB then we should add WMB types as official reference data via pipeline. These types cross-cut morphological types so I suggest:

MLI1

• MLI1 basket cell (also subclass basket cell)
• MLI1 stellate cell (...) MLI2
• MLI2 stellate cell (...)
• MLI2 - some name for additional morphology described.

Also worth adding comment to basket and stellate cell terms: "any MLIs, particularly those in the middle of the molecular layer, share morphological features with both basket and stellate cells (ref: Sultan, F. & Bower, J. M. Quantitative Golgi study of the rat cerebellar molecular layer interneurons using principal component analysis. J. Comp. Neurol. 393, 353–373 (1998))

Naming: Marker based might be better then numbered? Do any of markers hold up for mouse and human?

Mapping could be via markers described in paper, but also potentially via annotation transfer - see: https://github.com/Cellular-Semantics/whole_mouse_brain_ontology/issues/93

[RiveraAndrea83]

@RiveraAndrea83 need to create 2 terms for MLI1 and MLI2