update estimateAbundance, plotAbundanceCurve to work with mixed data

[ssnn]

estimateAbundance, plotAbundanceCurve to allow for mixed bulk and sc, H and L data. Counting will be done:

• For the sc part (cell_id exists), count unique cell ids within a clone_id.
• For the bulk part (no cell_id), count the number of sequences in the locus of interest (usually IGH). Keep the option to use dupcount.

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