Items for V2.0 (protein compatibility) to be ready for launch:
[x] get_anchor_stats: don't insist on SDs unless assay_type = "protein"
[x] default everything to assay_type = "rna"
[x] add spatialUpdate()
[x] add function deriveProfiles() based on Estep()
[ ] should "neg" be required if we're running protein? (If not, then make sure this is added to all exported functions. Default neg = NULL, then check it's not NULL if it's an RNA assay, and error informatively. If left as NULL for protein, shouldn't impact anything downstream.)
Items for V2.0 (protein compatibility) to be ready for launch: