Siletti - updates

[dosumis]

• Add subclusters to Siletti CAS taxonomy (following IDs on ABC!) #14
• add Neurotransmitters to Siletti CAS taxonomy (but not ontology mappings?) #15
• add location to CAS taxonomy (already curated for PCL) #12
• Curate annotation transfer from MTG to Siletti taxonomies #9
• Add author Categories to Siletti CAS  #23

Can we bundle all these into a single release?

[dosumis]

Progress - this notebooks shows addition of subclusters and annotation transfer for non-neuronal cells. Needs to be repeated for neurons:
https://github.com/dosumis/siletti_hacking/blob/main/Silleti_v2_hacking.ipynb

We could defer Neurotransmitters and location sumarries to a future version. Should be very easy to quickly add author categories from supp matt.